--- a/dom/canvas/WebGLContext.cpp
+++ b/dom/canvas/WebGLContext.cpp
@@ -212,16 +212,17 @@ WebGLContextOptions::WebGLContextOptions
         alpha = false;
 }
 
 WebGLContext::WebGLContext()
     : WebGLContextUnchecked(nullptr)
     , mBypassShaderValidation(false)
     , mGLMaxSamples(1)
     , mNeedsFakeNoAlpha(false)
+    , mNeedsFakeNoDepth(false)
     , mNeedsFakeNoStencil(false)
 {
     mGeneration = 0;
     mInvalidated = false;
     mCapturedFrameInvalidated = false;
     mShouldPresent = true;
     mResetLayer = true;
     mOptionsFrozen = false;
@@ -248,16 +249,17 @@ WebGLContext::WebGLContext()
     mViewportX = 0;
     mViewportY = 0;
     mViewportWidth = 0;
     mViewportHeight = 0;
 
     mDitherEnabled = 1;
     mRasterizerDiscardEnabled = 0; // OpenGL ES 3.0 spec p244
     mScissorTestEnabled = 0;
+    mDepthTestEnabled = 0;
     mStencilTestEnabled = 0;
 
     // initialize some GL values: we're going to get them from the GL and use them as the sizes of arrays,
     // so in case glGetIntegerv leaves them uninitialized because of a GL bug, we would have very weird crashes.
     mGLMaxVertexAttribs = 0;
     mGLMaxTextureUnits = 0;
     mGLMaxTextureSize = 0;
     mGLMaxTextureSizeLog2 = 0;
@@ -538,251 +540,244 @@ HasAcceleratedLayers(const nsCOMPtr<nsIG
         return true;
     gfxInfo->GetFeatureStatus(nsIGfxInfo::FEATURE_OPENGL_LAYERS, &status);
     if (status)
         return true;
 
     return false;
 }
 
-static already_AddRefed<GLContext>
-CreateHeadlessNativeGL(CreateContextFlags flags, const nsCOMPtr<nsIGfxInfo>& gfxInfo,
-                       WebGLContext* webgl)
-{
-    if (!(flags & CreateContextFlags::FORCE_ENABLE_HARDWARE) &&
-        IsFeatureInBlacklist(gfxInfo, nsIGfxInfo::FEATURE_WEBGL_OPENGL))
-    {
-        webgl->GenerateWarning("Refused to create native OpenGL context"
-                               " because of blacklisting.");
-        return nullptr;
-    }
-
-    nsRefPtr<GLContext> gl = gl::GLContextProvider::CreateHeadless(flags);
-    if (!gl) {
-        webgl->GenerateWarning("Error during native OpenGL init.");
-        return nullptr;
-    }
-    MOZ_ASSERT(!gl->IsANGLE());
-
-    return gl.forget();
-}
-
-// Note that we have a separate call for ANGLE and EGL, even though
-// right now, we get ANGLE implicitly by using EGL on Windows.
-// Eventually, we want to be able to pick ANGLE-EGL or native EGL.
-static already_AddRefed<GLContext>
-CreateHeadlessANGLE(CreateContextFlags flags, const nsCOMPtr<nsIGfxInfo>& gfxInfo,
-                    WebGLContext* webgl)
-{
-    nsRefPtr<GLContext> gl;
-
-#ifdef XP_WIN
-    gl = gl::GLContextProviderEGL::CreateHeadless(flags);
-    if (!gl) {
-        webgl->GenerateWarning("Error during ANGLE OpenGL init.");
-        return nullptr;
-    }
-    MOZ_ASSERT(gl->IsANGLE());
-#endif
-
-    return gl.forget();
-}
-
-static already_AddRefed<GLContext>
-CreateHeadlessEGL(CreateContextFlags flags, WebGLContext* webgl)
-{
-    nsRefPtr<GLContext> gl;
-
-#ifdef ANDROID
-    gl = gl::GLContextProviderEGL::CreateHeadless(flags);
-    if (!gl) {
-        webgl->GenerateWarning("Error during EGL OpenGL init.");
-        return nullptr;
-    }
-    MOZ_ASSERT(!gl->IsANGLE());
-#endif
-
-    return gl.forget();
-}
-
-static already_AddRefed<GLContext>
-CreateHeadlessGL(CreateContextFlags flags, const nsCOMPtr<nsIGfxInfo>& gfxInfo,
-                 WebGLContext* webgl)
-{
-    bool preferEGL = PR_GetEnv("MOZ_WEBGL_PREFER_EGL");
-    bool disableANGLE = Preferences::GetBool("webgl.disable-angle", false);
-
-    if (PR_GetEnv("MOZ_WEBGL_FORCE_OPENGL"))
-        disableANGLE = true;
-
-    if (!webgl->IsWebGL2()) {
-        flags |= CreateContextFlags::REQUIRE_COMPAT_PROFILE;
-    }
-
-    nsRefPtr<GLContext> gl;
-
-    if (preferEGL)
-        gl = CreateHeadlessEGL(flags, webgl);
-
-    if (!gl && !disableANGLE) {
-        gl = CreateHeadlessANGLE(flags, gfxInfo, webgl);
-    }
-
-    if (!gl) {
-        gl = CreateHeadlessNativeGL(flags, gfxInfo, webgl);
-    }
-
-    return gl.forget();
-}
-
-// Try to create a dummy offscreen with the given caps.
-static bool
-CreateOffscreenWithCaps(GLContext* gl, const SurfaceCaps& caps)
-{
-    gfx::IntSize dummySize(16, 16);
-    return gl->InitOffscreen(dummySize, caps);
-}
-
 static void
-PopulateCapFallbackQueue(const SurfaceCaps& baseCaps,
-                         std::queue<SurfaceCaps>* out_fallbackCaps)
+PopulateCapFallbackQueue(const gl::SurfaceCaps& baseCaps,
+                         std::queue<gl::SurfaceCaps>* out_fallbackCaps)
 {
     out_fallbackCaps->push(baseCaps);
 
     // Dropping antialias drops our quality, but not our correctness.
     // The user basically doesn't have to handle if this fails, they
     // just get reduced quality.
     if (baseCaps.antialias) {
-        SurfaceCaps nextCaps(baseCaps);
+        gl::SurfaceCaps nextCaps(baseCaps);
         nextCaps.antialias = false;
         PopulateCapFallbackQueue(nextCaps, out_fallbackCaps);
     }
 
     // If we have to drop one of depth or stencil, we'd prefer to keep
     // depth. However, the client app will need to handle if this
     // doesn't work.
     if (baseCaps.stencil) {
-        SurfaceCaps nextCaps(baseCaps);
+        gl::SurfaceCaps nextCaps(baseCaps);
         nextCaps.stencil = false;
         PopulateCapFallbackQueue(nextCaps, out_fallbackCaps);
     }
 
     if (baseCaps.depth) {
-        SurfaceCaps nextCaps(baseCaps);
+        gl::SurfaceCaps nextCaps(baseCaps);
         nextCaps.depth = false;
         PopulateCapFallbackQueue(nextCaps, out_fallbackCaps);
     }
 }
 
-static bool
-CreateOffscreen(GLContext* gl, const WebGLContextOptions& options,
-                const nsCOMPtr<nsIGfxInfo>& gfxInfo, WebGLContext* webgl,
-                layers::LayersBackend layersBackend,
-                layers::ISurfaceAllocator* surfAllocator)
+static gl::SurfaceCaps
+BaseCaps(const WebGLContextOptions& options, WebGLContext* webgl)
 {
-    SurfaceCaps baseCaps;
+    gl::SurfaceCaps baseCaps;
 
     baseCaps.color = true;
     baseCaps.alpha = options.alpha;
     baseCaps.antialias = options.antialias;
     baseCaps.depth = options.depth;
     baseCaps.premultAlpha = options.premultipliedAlpha;
     baseCaps.preserve = options.preserveDrawingBuffer;
     baseCaps.stencil = options.stencil;
 
     if (!baseCaps.alpha)
         baseCaps.premultAlpha = true;
 
-    if (gl->IsANGLE() ||
-        (gl->GetContextType() == GLContextType::GLX &&
-         layersBackend == LayersBackend::LAYERS_OPENGL))
-    {
-        // We can't use no-alpha formats on ANGLE yet because of:
-        // https://code.google.com/p/angleproject/issues/detail?id=764
-        // GLX only supports GL_RGBA pixmaps as well. Since we can't blit from
-        // an RGB FB to GLX's RGBA FB, force RGBA when surface sharing.
-        baseCaps.alpha = true;
-    }
-
     // we should really have this behind a
     // |gfxPlatform::GetPlatform()->GetScreenDepth() == 16| check, but
     // for now it's just behind a pref for testing/evaluation.
     baseCaps.bpp16 = Preferences::GetBool("webgl.prefer-16bpp", false);
 
 #ifdef MOZ_WIDGET_GONK
-    baseCaps.surfaceAllocator = surfAllocator;
+    do {
+        auto canvasElement = webgl->GetCanvas();
+        auto ownerDoc = canvasElement->OwnerDoc();
+        nsIWidget* docWidget = nsContentUtils::WidgetForDocument(ownerDoc);
+        if (!docWidget)
+            break;
+
+        layers::LayerManager* layerManager = docWidget->GetLayerManager();
+        if (!layerManager)
+            break;
+
+        // XXX we really want "AsSurfaceAllocator" here for generality
+        layers::ShadowLayerForwarder* forwarder = layerManager->AsShadowForwarder();
+        if (!forwarder)
+            break;
+
+        baseCaps.surfaceAllocator = static_cast<layers::ISurfaceAllocator*>(forwarder);
+    } while (false);
 #endif
 
     // Done with baseCaps construction.
 
     bool forceAllowAA = Preferences::GetBool("webgl.msaa-force", false);
+    nsCOMPtr<nsIGfxInfo> gfxInfo = services::GetGfxInfo();
     if (!forceAllowAA &&
         IsFeatureInBlacklist(gfxInfo, nsIGfxInfo::FEATURE_WEBGL_MSAA))
     {
         webgl->GenerateWarning("Disallowing antialiased backbuffers due"
                                " to blacklisting.");
         baseCaps.antialias = false;
     }
 
-    std::queue<SurfaceCaps> fallbackCaps;
+    return baseCaps;
+}
+
+////////////////////////////////////////
+
+static already_AddRefed<gl::GLContext>
+CreateGLWithEGL(const gl::SurfaceCaps& caps, gl::CreateContextFlags flags,
+                WebGLContext* webgl)
+{
+    RefPtr<GLContext> gl;
+#ifndef XP_MACOSX // Mac doesn't have GLContextProviderEGL.
+    gfx::IntSize dummySize(16, 16);
+    gl = gl::GLContextProviderEGL::CreateOffscreen(dummySize, caps,
+                                                                     flags);
+    if (!gl) {
+        webgl->GenerateWarning("Error during EGL OpenGL init.");
+        return nullptr;
+    }
+
+    if (gl->IsANGLE())
+        return nullptr;
+#endif // XP_MACOSX
+    return gl.forget();
+}
+
+static already_AddRefed<GLContext>
+CreateGLWithANGLE(const gl::SurfaceCaps& caps, gl::CreateContextFlags flags,
+                  WebGLContext* webgl)
+{
+    RefPtr<GLContext> gl;
+
+#ifdef XP_WIN
+    gfx::IntSize dummySize(16, 16);
+    gl = gl::GLContextProviderEGL::CreateOffscreen(dummySize, caps, flags);
+    if (!gl) {
+        webgl->GenerateWarning("Error during ANGLE OpenGL init.");
+        return nullptr;
+    }
+
+    if (!gl->IsANGLE())
+        return nullptr;
+#endif
+
+    return gl.forget();
+}
+
+static already_AddRefed<gl::GLContext>
+CreateGLWithDefault(const gl::SurfaceCaps& caps, gl::CreateContextFlags flags,
+                    WebGLContext* webgl)
+{
+    nsCOMPtr<nsIGfxInfo> gfxInfo = services::GetGfxInfo();
+
+    if (!(flags & CreateContextFlags::FORCE_ENABLE_HARDWARE) &&
+        IsFeatureInBlacklist(gfxInfo, nsIGfxInfo::FEATURE_WEBGL_OPENGL))
+    {
+        webgl->GenerateWarning("Refused to create native OpenGL context because of"
+                               " blacklisting.");
+        return nullptr;
+    }
+
+    gfx::IntSize dummySize(16, 16);
+    RefPtr<GLContext> gl = gl::GLContextProvider::CreateOffscreen(dummySize, caps, flags);
+    if (!gl) {
+        webgl->GenerateWarning("Error during native OpenGL init.");
+        return nullptr;
+    }
+
+    if (gl->IsANGLE())
+        return nullptr;
+
+    return gl.forget();
+}
+
+////////////////////////////////////////
+
+bool
+WebGLContext::CreateAndInitGLWith(FnCreateGL_T fnCreateGL,
+                                  const gl::SurfaceCaps& baseCaps,
+                                  gl::CreateContextFlags flags)
+{
+    MOZ_ASSERT(!gl);
+
+    std::queue<gl::SurfaceCaps> fallbackCaps;
     PopulateCapFallbackQueue(baseCaps, &fallbackCaps);
 
-    bool created = false;
+    gl = nullptr;
     while (!fallbackCaps.empty()) {
-        SurfaceCaps& caps = fallbackCaps.front();
+        gl::SurfaceCaps& caps = fallbackCaps.front();
 
-        created = CreateOffscreenWithCaps(gl, caps);
-        if (created)
+        gl = fnCreateGL(caps, flags, this);
+        if (gl)
             break;
 
         fallbackCaps.pop();
     }
+    if (!gl)
+        return false;
 
-    return created;
+    if (!InitAndValidateGL()) {
+        gl = nullptr;
+        return false;
+    }
+
+    return true;
 }
 
 bool
-WebGLContext::CreateOffscreenGL(bool forceEnabled)
+WebGLContext::CreateAndInitGL(bool forceEnabled)
 {
-    nsCOMPtr<nsIGfxInfo> gfxInfo = services::GetGfxInfo();
+    bool preferEGL = PR_GetEnv("MOZ_WEBGL_PREFER_EGL");
+    bool disableANGLE = Preferences::GetBool("webgl.disable-angle", false);
+
+    if (PR_GetEnv("MOZ_WEBGL_FORCE_OPENGL"))
+        disableANGLE = true;
 
-    layers::ISurfaceAllocator* surfAllocator = nullptr;
-#ifdef MOZ_WIDGET_GONK
-    nsIWidget* docWidget = nsContentUtils::WidgetForDocument(mCanvasElement->OwnerDoc());
-    if (docWidget) {
-        layers::LayerManager* layerManager = docWidget->GetLayerManager();
-        if (layerManager) {
-            // XXX we really want "AsSurfaceAllocator" here for generality
-            layers::ShadowLayerForwarder* forwarder = layerManager->AsShadowForwarder();
-            if (forwarder)
-                surfAllocator = static_cast<layers::ISurfaceAllocator*>(forwarder);
-        }
-    }
-#endif
+    gl::CreateContextFlags flags = gl::CreateContextFlags::NONE;
+    if (forceEnabled) flags |= gl::CreateContextFlags::FORCE_ENABLE_HARDWARE;
+    if (!IsWebGL2())  flags |= gl::CreateContextFlags::REQUIRE_COMPAT_PROFILE;
+
+    const gl::SurfaceCaps baseCaps = BaseCaps(mOptions, this);
+
+    MOZ_ASSERT(!gl);
 
-    CreateContextFlags flags = forceEnabled ? CreateContextFlags::FORCE_ENABLE_HARDWARE :
-                                              CreateContextFlags::NONE;
+    if (preferEGL) {
+        if (CreateAndInitGLWith(CreateGLWithEGL, baseCaps, flags))
+            return true;
+    }
 
-    gl = CreateHeadlessGL(flags, gfxInfo, this);
-
-    do {
-        if (!gl)
-            break;
+    MOZ_ASSERT(!gl);
 
-        if (!CreateOffscreen(gl, mOptions, gfxInfo, this,
-                             GetCompositorBackendType(), surfAllocator))
-            break;
+    if (!disableANGLE) {
+        if (CreateAndInitGLWith(CreateGLWithANGLE, baseCaps, flags))
+            return true;
+    }
+
+    MOZ_ASSERT(!gl);
 
-        if (!InitAndValidateGL())
-            break;
-
+    if (CreateAndInitGLWith(CreateGLWithDefault, baseCaps, flags))
         return true;
-    } while (false);
 
+    MOZ_ASSERT(!gl);
     gl = nullptr;
+
     return false;
 }
 
 // Fallback for resizes:
 bool
 WebGLContext::ResizeBackbuffer(uint32_t requestedWidth,
                                uint32_t requestedHeight)
 {
@@ -936,22 +931,25 @@ WebGLContext::SetDimensions(int32_t sign
             return NS_ERROR_FAILURE;
         }
     }
 
     // Alright, now let's start trying.
     bool forceEnabled = Preferences::GetBool("webgl.force-enabled", false);
     ScopedGfxFeatureReporter reporter("WebGL", forceEnabled);
 
-    if (!CreateOffscreenGL(forceEnabled)) {
+    MOZ_ASSERT(!gl);
+    if (!CreateAndInitGL(forceEnabled)) {
         GenerateWarning("WebGL creation failed.");
         return NS_ERROR_FAILURE;
     }
     MOZ_ASSERT(gl);
 
+    MOZ_ASSERT_IF(mOptions.alpha, gl->Caps().alpha);
+
     if (!ResizeBackbuffer(width, height)) {
         GenerateWarning("Initializing WebGL backbuffer failed.");
         return NS_ERROR_FAILURE;
     }
 
 #ifdef DEBUG
     if (gl->DebugMode())
         printf_stderr("--- WebGL context created: %p\n", gl.get());
@@ -960,24 +958,30 @@ WebGLContext::SetDimensions(int32_t sign
     mResetLayer = true;
     mOptionsFrozen = true;
 
     // Update our internal stuff:
     if (gl->WorkAroundDriverBugs()) {
         if (!mOptions.alpha && gl->Caps().alpha)
             mNeedsFakeNoAlpha = true;
 
-        // ANGLE doesn't quite handle this properly.
-        if (gl->Caps().depth && !gl->Caps().stencil && gl->IsANGLE())
+        if (!mOptions.depth && gl->Caps().depth)
+            mNeedsFakeNoDepth = true;
+
+        if (!mOptions.stencil && gl->Caps().stencil)
             mNeedsFakeNoStencil = true;
     }
 
     // Update mOptions.
-    mOptions.depth = gl->Caps().depth;
-    mOptions.stencil = gl->Caps().stencil;
+    if (!gl->Caps().depth)
+        mOptions.depth = false;
+
+    if (!gl->Caps().stencil)
+        mOptions.stencil = false;
+
     mOptions.antialias = gl->Caps().antialias;
 
     MakeContextCurrent();
 
     gl->fViewport(0, 0, mWidth, mHeight);
     mViewportWidth = mWidth;
     mViewportHeight = mHeight;
 
@@ -993,20 +997,26 @@ WebGLContext::SetDimensions(int32_t sign
     // Clear immediately, because we need to present the cleared initial
     // buffer.
     mBackbufferNeedsClear = true;
     ClearBackbufferIfNeeded();
 
     mShouldPresent = true;
 
     MOZ_ASSERT(gl->Caps().color);
+
     MOZ_ASSERT_IF(!mNeedsFakeNoAlpha, gl->Caps().alpha == mOptions.alpha);
     MOZ_ASSERT_IF(mNeedsFakeNoAlpha, !mOptions.alpha && gl->Caps().alpha);
-    MOZ_ASSERT(gl->Caps().depth == mOptions.depth);
-    MOZ_ASSERT(gl->Caps().stencil == mOptions.stencil);
+
+    MOZ_ASSERT_IF(!mNeedsFakeNoDepth, gl->Caps().depth == mOptions.depth);
+    MOZ_ASSERT_IF(mNeedsFakeNoDepth, !mOptions.depth && gl->Caps().depth);
+
+    MOZ_ASSERT_IF(!mNeedsFakeNoStencil, gl->Caps().stencil == mOptions.stencil);
+    MOZ_ASSERT_IF(mNeedsFakeNoStencil, !mOptions.stencil && gl->Caps().stencil);
+
     MOZ_ASSERT(gl->Caps().antialias == mOptions.antialias);
     MOZ_ASSERT(gl->Caps().preserve == mOptions.preserveDrawingBuffer);
 
     AssertCachedBindings();
     AssertCachedState();
 
     reporter.SetSuccessful();
     return NS_OK;
@@ -1871,37 +1881,44 @@ RoundedToNextMultipleOf(CheckedUint32 x,
     return ((x + y - 1) / y) * y;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 
 WebGLContext::ScopedMaskWorkaround::ScopedMaskWorkaround(WebGLContext& webgl)
     : mWebGL(webgl)
     , mFakeNoAlpha(ShouldFakeNoAlpha(webgl))
+    , mFakeNoDepth(ShouldFakeNoDepth(webgl))
     , mFakeNoStencil(ShouldFakeNoStencil(webgl))
 {
     if (mFakeNoAlpha) {
         mWebGL.gl->fColorMask(mWebGL.mColorWriteMask[0],
                               mWebGL.mColorWriteMask[1],
                               mWebGL.mColorWriteMask[2],
                               false);
     }
+    if (mFakeNoDepth) {
+        mWebGL.gl->fDisable(LOCAL_GL_DEPTH_TEST);
+    }
     if (mFakeNoStencil) {
         mWebGL.gl->fDisable(LOCAL_GL_STENCIL_TEST);
     }
 }
 
 WebGLContext::ScopedMaskWorkaround::~ScopedMaskWorkaround()
 {
     if (mFakeNoAlpha) {
         mWebGL.gl->fColorMask(mWebGL.mColorWriteMask[0],
                               mWebGL.mColorWriteMask[1],
                               mWebGL.mColorWriteMask[2],
                               mWebGL.mColorWriteMask[3]);
     }
+    if (mFakeNoDepth) {
+        mWebGL.gl->fEnable(LOCAL_GL_DEPTH_TEST);
+    }
     if (mFakeNoStencil) {
         mWebGL.gl->fEnable(LOCAL_GL_STENCIL_TEST);
     }
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // XPCOM goop
 

--- a/dom/canvas/WebGLContext.h
+++ b/dom/canvas/WebGLContext.h
@@ -3,32 +3,34 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef WEBGLCONTEXT_H_
 #define WEBGLCONTEXT_H_
 
 #include <stdarg.h>
 
+#include "GLContextTypes.h"
 #include "GLDefs.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/CheckedInt.h"
 #include "mozilla/dom/HTMLCanvasElement.h"
 #include "mozilla/dom/TypedArray.h"
 #include "mozilla/EnumeratedArray.h"
 #include "mozilla/ErrorResult.h"
 #include "mozilla/gfx/2D.h"
 #include "mozilla/LinkedList.h"
 #include "mozilla/UniquePtr.h"
 #include "mozilla/WeakPtr.h"
 #include "nsCycleCollectionNoteChild.h"
 #include "nsICanvasRenderingContextInternal.h"
 #include "nsLayoutUtils.h"
 #include "nsTArray.h"
 #include "nsWrapperCache.h"
+#include "SurfaceTypes.h"
 
 #ifdef XP_MACOSX
 #include "ForceDiscreteGPUHelperCGL.h"
 #endif
 
 // Local
 #include "WebGLContextUnchecked.h"
 #include "WebGLFormats.h"
@@ -807,16 +809,17 @@ public:
                              JS::MutableHandle<JS::Value> retval);
     bool IsEnabled(GLenum cap);
 
 private:
     // State tracking slots
     realGLboolean mDitherEnabled;
     realGLboolean mRasterizerDiscardEnabled;
     realGLboolean mScissorTestEnabled;
+    realGLboolean mDepthTestEnabled;
     realGLboolean mStencilTestEnabled;
 
     bool ValidateCapabilityEnum(GLenum cap, const char* info);
     realGLboolean* GetStateTrackingSlot(GLenum cap);
 
 // -----------------------------------------------------------------------------
 // Texture funcions (WebGLContextTextures.cpp)
 public:
@@ -1148,21 +1151,29 @@ protected:
     // -------------------------------------------------------------------------
     // WebGL 2 specifics (implemented in WebGL2Context.cpp)
 public:
     virtual bool IsWebGL2() const = 0;
 
 protected:
     bool InitWebGL2();
 
+    bool CreateAndInitGL(bool forceEnabled);
+    bool ResizeBackbuffer(uint32_t width, uint32_t height);
+
+    typedef already_AddRefed<gl::GLContext> FnCreateGL_T(const gl::SurfaceCaps& caps,
+                                                         gl::CreateContextFlags flags,
+                                                         WebGLContext* webgl);
+
+    bool CreateAndInitGLWith(FnCreateGL_T fnCreateGL, const gl::SurfaceCaps& baseCaps,
+                             gl::CreateContextFlags flags);
+
     // -------------------------------------------------------------------------
     // Validation functions (implemented in WebGLContextValidate.cpp)
-    bool CreateOffscreenGL(bool forceEnabled);
     bool InitAndValidateGL();
-    bool ResizeBackbuffer(uint32_t width, uint32_t height);
     bool ValidateBlendEquationEnum(GLenum cap, const char* info);
     bool ValidateBlendFuncDstEnum(GLenum mode, const char* info);
     bool ValidateBlendFuncSrcEnum(GLenum mode, const char* info);
     bool ValidateBlendFuncEnumsCompatibility(GLenum sfactor, GLenum dfactor,
                                              const char* info);
     bool ValidateDataOffsetSize(WebGLintptr offset, WebGLsizeiptr size, WebGLsizeiptr bufferSize, const char* info);
     bool ValidateDataRanges(WebGLintptr readOffset, WebGLintptr writeOffset, WebGLsizeiptr size, const char* info);
     bool ValidateTextureTargetEnum(GLenum target, const char* info);
@@ -1438,31 +1449,40 @@ protected:
     int mMaxWarnings;
     bool mAlreadyWarnedAboutFakeVertexAttrib0;
 
     bool ShouldGenerateWarnings() const;
 
     uint64_t mLastUseIndex;
 
     bool mNeedsFakeNoAlpha;
+    bool mNeedsFakeNoDepth;
     bool mNeedsFakeNoStencil;
 
     struct ScopedMaskWorkaround {
         WebGLContext& mWebGL;
         const bool mFakeNoAlpha;
+        const bool mFakeNoDepth;
         const bool mFakeNoStencil;
 
         static bool ShouldFakeNoAlpha(WebGLContext& webgl) {
             // We should only be doing this if we're about to draw to the backbuffer, but
             // the backbuffer needs to have this fake-no-alpha workaround.
             return !webgl.mBoundDrawFramebuffer &&
                    webgl.mNeedsFakeNoAlpha &&
                    webgl.mColorWriteMask[3] != false;
         }
 
+        static bool ShouldFakeNoDepth(WebGLContext& webgl) {
+            // We should only be doing this if we're about to draw to the backbuffer.
+            return !webgl.mBoundDrawFramebuffer &&
+                   webgl.mNeedsFakeNoDepth &&
+                   webgl.mDepthTestEnabled;
+        }
+
         static bool ShouldFakeNoStencil(WebGLContext& webgl) {
             // We should only be doing this if we're about to draw to the backbuffer.
             return !webgl.mBoundDrawFramebuffer &&
                    webgl.mNeedsFakeNoStencil &&
                    webgl.mStencilTestEnabled;
         }
 
         explicit ScopedMaskWorkaround(WebGLContext& webgl);

--- a/dom/canvas/WebGLContextState.cpp
+++ b/dom/canvas/WebGLContextState.cpp
@@ -355,20 +355,26 @@ WebGLContext::GetParameter(JSContext* cx
         case LOCAL_GL_SAMPLE_BUFFERS:
         case LOCAL_GL_SAMPLES:
         case LOCAL_GL_MAX_VERTEX_ATTRIBS:
         case LOCAL_GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS:
         case LOCAL_GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS:
         case LOCAL_GL_MAX_TEXTURE_IMAGE_UNITS:
         case LOCAL_GL_RED_BITS:
         case LOCAL_GL_GREEN_BITS:
-        case LOCAL_GL_BLUE_BITS:
+        case LOCAL_GL_BLUE_BITS: {
+            GLint i = 0;
+            gl->fGetIntegerv(pname, &i);
+            return JS::Int32Value(i);
+        }
         case LOCAL_GL_DEPTH_BITS: {
             GLint i = 0;
-            gl->fGetIntegerv(pname, &i);
+            if (!mNeedsFakeNoDepth) {
+                gl->fGetIntegerv(pname, &i);
+            }
             return JS::Int32Value(i);
         }
         case LOCAL_GL_ALPHA_BITS: {
             GLint i = 0;
             if (!mNeedsFakeNoAlpha) {
                 gl->fGetIntegerv(pname, &i);
             }
             return JS::Int32Value(i);
@@ -617,16 +623,18 @@ WebGLContext::ValidateCapabilityEnum(GLe
             return false;
     }
 }
 
 realGLboolean*
 WebGLContext::GetStateTrackingSlot(GLenum cap)
 {
     switch (cap) {
+        case LOCAL_GL_DEPTH_TEST:
+            return &mDepthTestEnabled;
         case LOCAL_GL_DITHER:
             return &mDitherEnabled;
         case LOCAL_GL_RASTERIZER_DISCARD:
             return &mRasterizerDiscardEnabled;
         case LOCAL_GL_SCISSOR_TEST:
             return &mScissorTestEnabled;
         case LOCAL_GL_STENCIL_TEST:
             return &mStencilTestEnabled;

--- a/dom/canvas/WebGLContextUtils.cpp
+++ b/dom/canvas/WebGLContextUtils.cpp
@@ -1170,16 +1170,17 @@ WebGLContext::AssertCachedState()
 
     // extensions
     if (IsExtensionEnabled(WebGLExtensionID::WEBGL_draw_buffers)) {
         AssertUintParamCorrect(gl, LOCAL_GL_MAX_COLOR_ATTACHMENTS, mGLMaxColorAttachments);
         AssertUintParamCorrect(gl, LOCAL_GL_MAX_DRAW_BUFFERS, mGLMaxDrawBuffers);
     }
 
     // Draw state
+    MOZ_ASSERT(gl->fIsEnabled(LOCAL_GL_DEPTH_TEST) == mDepthTestEnabled);
     MOZ_ASSERT(gl->fIsEnabled(LOCAL_GL_DITHER) == mDitherEnabled);
     MOZ_ASSERT_IF(IsWebGL2(),
                   gl->fIsEnabled(LOCAL_GL_RASTERIZER_DISCARD) == mRasterizerDiscardEnabled);
     MOZ_ASSERT(gl->fIsEnabled(LOCAL_GL_SCISSOR_TEST) == mScissorTestEnabled);
     MOZ_ASSERT(gl->fIsEnabled(LOCAL_GL_STENCIL_TEST) == mStencilTestEnabled);
 
     realGLboolean colorWriteMask[4] = {0, 0, 0, 0};
     gl->fGetBooleanv(LOCAL_GL_COLOR_WRITEMASK, colorWriteMask);

--- a/dom/media/platforms/android/AndroidDecoderModule.cpp
+++ b/dom/media/platforms/android/AndroidDecoderModule.cpp
@@ -95,17 +95,17 @@ public:
       return nullptr;
     }
 
     EGLint attribs[] = {
       LOCAL_EGL_IMAGE_PRESERVED_KHR, LOCAL_EGL_TRUE,
       LOCAL_EGL_NONE, LOCAL_EGL_NONE
     };
 
-    EGLContext eglContext = static_cast<GLContextEGL*>(mGLContext.get())->GetEGLContext();
+    EGLContext eglContext = static_cast<GLContextEGL*>(mGLContext.get())->mContext;
     EGLImage eglImage = sEGLLibrary.fCreateImage(EGL_DISPLAY(), eglContext,
                                                  LOCAL_EGL_GL_TEXTURE_2D_KHR,
                                                  (EGLClientBuffer)tex, attribs);
     mGLContext->fDeleteTextures(1, &tex);
 
     return eglImage;
   }
 

--- a/dom/plugins/base/android/ANPOpenGL.cpp
+++ b/dom/plugins/base/android/ANPOpenGL.cpp
@@ -23,17 +23,17 @@ typedef nsNPAPIPluginInstance::TextureIn
 static ANPEGLContext anp_opengl_acquireContext(NPP instance) {
     nsNPAPIPluginInstance* pinst = static_cast<nsNPAPIPluginInstance*>(instance->ndata);
 
     GLContext* context = pinst->GLContext();
     if (!context)
         return nullptr;
 
     context->MakeCurrent();
-    return GLContextEGL::Cast(context)->GetEGLContext();
+    return GLContextEGL::Cast(context)->mContext;
 }
 
 static ANPTextureInfo anp_opengl_lockTexture(NPP instance) {
     nsNPAPIPluginInstance* pinst = static_cast<nsNPAPIPluginInstance*>(instance->ndata);
 
     TextureInfo pluginInfo = pinst->LockContentTexture();
 
     ANPTextureInfo info;

--- a/gfx/gl/EGLUtils.cpp
+++ b/gfx/gl/EGLUtils.cpp
@@ -18,17 +18,17 @@ DoesEGLContextSupportSharingWithEGLImage
 }
 
 EGLImage
 CreateEGLImage(GLContext* gl, GLuint tex)
 {
     MOZ_ASSERT(DoesEGLContextSupportSharingWithEGLImage(gl));
 
     EGLClientBuffer clientBuffer = (EGLClientBuffer)((uint64_t)tex);
-    EGLContext eglContext = GLContextEGL::Cast(gl)->GetEGLContext();
+    EGLContext eglContext = GLContextEGL::Cast(gl)->mContext;
     EGLImage image = sEGLLibrary.fCreateImage(EGL_DISPLAY(),
                                               eglContext,
                                               LOCAL_EGL_GL_TEXTURE_2D,
                                               clientBuffer,
                                               nullptr);
     return image;
 }
 
@@ -37,17 +37,17 @@ CreateEGLImage(GLContext* gl, GLuint tex
 
 /*static*/ EGLImageWrapper*
 EGLImageWrapper::Create(GLContext* gl, GLuint tex)
 {
     MOZ_ASSERT(DoesEGLContextSupportSharingWithEGLImage(gl));
 
     GLLibraryEGL& library = sEGLLibrary;
     EGLDisplay display = EGL_DISPLAY();
-    EGLContext eglContext = GLContextEGL::Cast(gl)->GetEGLContext();
+    EGLContext eglContext = GLContextEGL::Cast(gl)->mContext;
     EGLClientBuffer clientBuffer = (EGLClientBuffer)((uint64_t)tex);
     EGLImage image = library.fCreateImage(display,
                                           eglContext,
                                           LOCAL_EGL_GL_TEXTURE_2D,
                                           clientBuffer,
                                           nullptr);
     if (!image) {
 #ifdef DEBUG

--- a/gfx/gl/GLContext.cpp
+++ b/gfx/gl/GLContext.cpp
@@ -301,17 +301,16 @@ GLContext::GLContext(const SurfaceCaps& 
     mIsOffscreen(isOffscreen),
     mContextLost(false),
     mVersion(0),
     mProfile(ContextProfile::Unknown),
     mVendor(GLVendor::Other),
     mRenderer(GLRenderer::Other),
     mHasRobustness(false),
     mTopError(LOCAL_GL_NO_ERROR),
-    mLocalErrorScope(nullptr),
     mSharedContext(sharedContext),
     mCaps(caps),
     mScreen(nullptr),
     mLockedSurface(nullptr),
     mMaxTextureSize(0),
     mMaxCubeMapTextureSize(0),
     mMaxTextureImageSize(0),
     mMaxRenderbufferSize(0),

--- a/gfx/gl/GLContext.h
+++ b/gfx/gl/GLContext.h
@@ -2,22 +2,23 @@
 /* vim: set ts=8 sts=4 et sw=4 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef GLCONTEXT_H_
 #define GLCONTEXT_H_
 
-#include <stdio.h>
-#include <stdint.h>
+#include <bitset>
 #include <ctype.h>
+#include <stdint.h>
+#include <stdio.h>
 #include <map>
-#include <bitset>
 #include <queue>
+#include <stack>
 
 #ifdef DEBUG
 #include <string.h>
 #endif
 
 #ifdef WIN32
 #include <windows.h>
 #endif
@@ -614,31 +615,30 @@ public:
         return err;
     }
 
     ////////////////////////////////////
     // Use this safer option.
     class LocalErrorScope;
 
 private:
-    LocalErrorScope* mLocalErrorScope;
+    std::stack<const LocalErrorScope*> mLocalErrorScopeStack;
 
 public:
     class LocalErrorScope {
         GLContext& mGL;
         GLenum mOldTop;
         bool mHasBeenChecked;
 
     public:
         explicit LocalErrorScope(GLContext& gl)
             : mGL(gl)
             , mHasBeenChecked(false)
         {
-            MOZ_ASSERT(!mGL.mLocalErrorScope);
-            mGL.mLocalErrorScope = this;
+            mGL.mLocalErrorScopeStack.push(this);
 
             mGL.FlushErrors();
 
             mOldTop = mGL.mTopError;
             mGL.mTopError = LOCAL_GL_NO_ERROR;
         }
 
         GLenum GetError() {
@@ -648,20 +648,20 @@ public:
             return mGL.fGetError();
         }
 
         ~LocalErrorScope() {
             MOZ_ASSERT(mHasBeenChecked);
 
             MOZ_ASSERT(mGL.fGetError() == LOCAL_GL_NO_ERROR);
 
+            MOZ_ASSERT(mGL.mLocalErrorScopeStack.top() == this);
+            mGL.mLocalErrorScopeStack.pop();
+
             mGL.mTopError = mOldTop;
-
-            MOZ_ASSERT(mGL.mLocalErrorScope == this);
-            mGL.mLocalErrorScope = nullptr;
         }
     };
 
     bool GetPotentialInteger(GLenum pname, GLint* param) {
         LocalErrorScope localError(*this);
 
         fGetIntegerv(pname, param);
 
@@ -733,17 +733,17 @@ private:
             GLenum err = FlushErrors();
 
             if (DebugMode() & DebugTrace) {
                 printf_stderr("[gl:%p] < %s [%s (0x%04x)]\n", this, funcName,
                               GLErrorToString(err), err);
             }
 
             if (err != LOCAL_GL_NO_ERROR &&
-                !mLocalErrorScope)
+                !mLocalErrorScopeStack.size())
             {
                 printf_stderr("[gl:%p] %s: Generated unexpected %s error."
                               " (0x%04x)\n", this, funcName,
                               GLErrorToString(err), err);
 
                 if (DebugMode() & DebugAbortOnError)
                     MOZ_CRASH("MOZ_GL_DEBUG_ABORT_ON_ERROR");
             }

--- a/gfx/gl/GLContextEGL.h
+++ b/gfx/gl/GLContextEGL.h
@@ -87,45 +87,46 @@ public:
     virtual bool SetupLookupFunction() override;
 
     virtual bool SwapBuffers() override;
 
     // hold a reference to the given surface
     // for the lifetime of this context.
     void HoldSurface(gfxASurface *aSurf);
 
-    EGLContext GetEGLContext() {
-        return mContext;
-    }
-
-    EGLSurface GetEGLSurface() {
+    EGLSurface GetEGLSurface() const {
         return mSurface;
     }
 
-    EGLDisplay GetEGLDisplay() {
-        return EGL_DISPLAY();
+    EGLDisplay GetEGLDisplay() const {
+        return sEGLLibrary.Display();
     }
 
     bool BindTex2DOffscreen(GLContext *aOffscreen);
     void UnbindTex2DOffscreen(GLContext *aOffscreen);
     void BindOffscreenFramebuffer();
 
     static already_AddRefed<GLContextEGL>
     CreateEGLPixmapOffscreenContext(const gfx::IntSize& size);
 
     static already_AddRefed<GLContextEGL>
-    CreateEGLPBufferOffscreenContext(const gfx::IntSize& size);
+    CreateEGLPBufferOffscreenContext(const gfx::IntSize& size,
+                                     const SurfaceCaps& minCaps);
 
 protected:
     friend class GLContextProviderEGL;
 
-    EGLConfig  mConfig;
+public:
+    const EGLConfig  mConfig;
+protected:
     EGLSurface mSurface;
+public:
+    const EGLContext mContext;
+protected:
     EGLSurface mSurfaceOverride;
-    EGLContext mContext;
     nsRefPtr<gfxASurface> mThebesSurface;
     bool mBound;
 
     bool mIsPBuffer;
     bool mIsDoubleBuffered;
     bool mCanBindToTexture;
     bool mShareWithEGLImage;
     bool mOwnsContext;

--- a/gfx/gl/GLContextProvider.h
+++ b/gfx/gl/GLContextProvider.h
@@ -4,84 +4,71 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef GLCONTEXTPROVIDER_H_
 #define GLCONTEXTPROVIDER_H_
 
 #include "GLContextTypes.h"
 #include "nsAutoPtr.h"
 #include "SurfaceTypes.h"
-#include "mozilla/TypedEnumBits.h"
 
 #include "nsSize.h" // for gfx::IntSize (needed by GLContextProviderImpl.h below)
 
 class nsIWidget;
 
 namespace mozilla {
 namespace gl {
 
-enum class CreateContextFlags : int8_t {
-    NONE = 0,
-    REQUIRE_COMPAT_PROFILE = 1 << 0,
-    // Force the use of hardware backed GL, don't allow software implementations.
-    FORCE_ENABLE_HARDWARE = 1 << 1,
-    /* Don't force discrete GPU to be used (if applicable) */
-    ALLOW_OFFLINE_RENDERER =  1 << 2,
-};
-MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(CreateContextFlags)
-
 #define IN_GL_CONTEXT_PROVIDER_H
 
 // Null is always there
 #define GL_CONTEXT_PROVIDER_NAME GLContextProviderNull
 #include "GLContextProviderImpl.h"
 #undef GL_CONTEXT_PROVIDER_NAME
 
 #ifdef XP_WIN
-#define GL_CONTEXT_PROVIDER_NAME GLContextProviderWGL
-#include "GLContextProviderImpl.h"
-#undef GL_CONTEXT_PROVIDER_NAME
-#define GL_CONTEXT_PROVIDER_DEFAULT GLContextProviderWGL
-#define DEFAULT_IMPL WGL
+  #define GL_CONTEXT_PROVIDER_NAME GLContextProviderWGL
+  #include "GLContextProviderImpl.h"
+  #undef GL_CONTEXT_PROVIDER_NAME
+  #define GL_CONTEXT_PROVIDER_DEFAULT GLContextProviderWGL
+  #define DEFAULT_IMPL WGL
 #endif
 
 #ifdef XP_MACOSX
-#define GL_CONTEXT_PROVIDER_NAME GLContextProviderCGL
-#include "GLContextProviderImpl.h"
-#undef GL_CONTEXT_PROVIDER_NAME
-#define GL_CONTEXT_PROVIDER_DEFAULT GLContextProviderCGL
+  #define GL_CONTEXT_PROVIDER_NAME GLContextProviderCGL
+  #include "GLContextProviderImpl.h"
+  #undef GL_CONTEXT_PROVIDER_NAME
+  #define GL_CONTEXT_PROVIDER_DEFAULT GLContextProviderCGL
 #endif
 
-#if defined(ANDROID) || defined(XP_WIN)
+#if defined(MOZ_X11)
+  #define GL_CONTEXT_PROVIDER_NAME GLContextProviderGLX
+  #include "GLContextProviderImpl.h"
+  #undef GL_CONTEXT_PROVIDER_NAME
+  #define GL_CONTEXT_PROVIDER_DEFAULT GLContextProviderGLX
+#endif
+
 #define GL_CONTEXT_PROVIDER_NAME GLContextProviderEGL
 #include "GLContextProviderImpl.h"
 #undef GL_CONTEXT_PROVIDER_NAME
 #ifndef GL_CONTEXT_PROVIDER_DEFAULT
-#define GL_CONTEXT_PROVIDER_DEFAULT GLContextProviderEGL
-#endif
+  #define GL_CONTEXT_PROVIDER_DEFAULT GLContextProviderEGL
 #endif
 
 #ifdef MOZ_GL_PROVIDER
-#define GL_CONTEXT_PROVIDER_NAME MOZ_GL_PROVIDER
-#include "GLContextProviderImpl.h"
-#undef GL_CONTEXT_PROVIDER_NAME
-#define GL_CONTEXT_PROVIDER_DEFAULT MOZ_GL_PROVIDER
-#endif
-
-#if defined(MOZ_X11) && !defined(GL_CONTEXT_PROVIDER_DEFAULT)
-#define GL_CONTEXT_PROVIDER_NAME GLContextProviderGLX
-#include "GLContextProviderImpl.h"
-#undef GL_CONTEXT_PROVIDER_NAME
-#define GL_CONTEXT_PROVIDER_DEFAULT GLContextProviderGLX
+  #define GL_CONTEXT_PROVIDER_NAME MOZ_GL_PROVIDER
+  #include "GLContextProviderImpl.h"
+  #undef GL_CONTEXT_PROVIDER_NAME
+  #define GL_CONTEXT_PROVIDER_DEFAULT MOZ_GL_PROVIDER
 #endif
 
 #ifdef GL_CONTEXT_PROVIDER_DEFAULT
-typedef GL_CONTEXT_PROVIDER_DEFAULT GLContextProvider;
+  typedef GL_CONTEXT_PROVIDER_DEFAULT GLContextProvider;
 #else
-typedef GLContextProviderNull GLContextProvider;
+  typedef GLContextProviderNull GLContextProvider;
 #endif
 
 #undef IN_GL_CONTEXT_PROVIDER_H
 
 } // namespace gl
 } // namespace mozilla
 
 #endif

--- a/gfx/gl/GLContextProviderCGL.mm
+++ b/gfx/gl/GLContextProviderCGL.mm
@@ -312,26 +312,27 @@ GLContextProviderCGL::CreateHeadless(Cre
         return nullptr;
     }
 
     return gl.forget();
 }
 
 already_AddRefed<GLContext>
 GLContextProviderCGL::CreateOffscreen(const IntSize& size,
-                                      const SurfaceCaps& caps,
+                                      const SurfaceCaps& minCaps,
                                       CreateContextFlags flags)
 {
-    nsRefPtr<GLContext> glContext = CreateHeadless(flags);
-    if (!glContext->InitOffscreen(size, caps)) {
-        NS_WARNING("Failed during InitOffscreen.");
+    RefPtr<GLContext> gl = CreateHeadless(flags);
+    if (!gl)
         return nullptr;
-    }
 
-    return glContext.forget();
+    if (!gl->InitOffscreen(size, minCaps))
+        return nullptr;
+
+    return gl.forget();
 }
 
 static nsRefPtr<GLContext> gGlobalContext;
 
 GLContext*
 GLContextProviderCGL::GetGlobalContext()
 {
     if (!sCGLLibrary.EnsureInitialized()) {

--- a/gfx/gl/GLContextProviderEGL.cpp
+++ b/gfx/gl/GLContextProviderEGL.cpp
@@ -1,123 +1,115 @@
 /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#include "mozilla/ArrayUtils.h"
-
-#include "GLContextEGL.h"
-
-#if defined(XP_UNIX)
-
-#ifdef MOZ_WIDGET_GTK
-#include <gdk/gdkx.h>
-// we're using default display for now
-#define GET_NATIVE_WINDOW(aWidget) (EGLNativeWindowType)GDK_WINDOW_XID((GdkWindow *) aWidget->GetNativeData(NS_NATIVE_WINDOW))
+#if defined(MOZ_WIDGET_GTK)
+    #include <gdk/gdkx.h>
+    // we're using default display for now
+    #define GET_NATIVE_WINDOW(aWidget) ((EGLNativeWindowType)GDK_WINDOW_XID((GdkWindow*)aWidget->GetNativeData(NS_NATIVE_WINDOW)))
 #elif defined(MOZ_WIDGET_QT)
-#define GET_NATIVE_WINDOW(aWidget) (EGLNativeWindowType)(aWidget->GetNativeData(NS_NATIVE_SHAREABLE_WINDOW))
-#elif defined(MOZ_WIDGET_GONK)
-#define GET_NATIVE_WINDOW(aWidget) ((EGLNativeWindowType)aWidget->GetNativeData(NS_NATIVE_WINDOW))
-#include "libdisplay/GonkDisplay.h"
-#include "nsWindow.h"
-#include "nsScreenManagerGonk.h"
-#endif
-
-#if defined(ANDROID)
-/* from widget */
-#if defined(MOZ_WIDGET_ANDROID)
-#include "AndroidBridge.h"
-#endif
-
-#include <android/log.h>
-#define LOG(args...)  __android_log_print(ANDROID_LOG_INFO, "Gonk" , ## args)
-
-# if defined(MOZ_WIDGET_GONK)
-#  include "cutils/properties.h"
-#  include <ui/GraphicBuffer.h>
-
-using namespace android;
-# endif
-
-#endif
-
-#define GLES2_LIB "libGLESv2.so"
-#define GLES2_LIB2 "libGLESv2.so.2"
-
-#elif defined(XP_WIN)
-
-#include "nsIFile.h"
-
-#define GLES2_LIB "libGLESv2.dll"
-
-#ifndef WIN32_LEAN_AND_MEAN
-#define WIN32_LEAN_AND_MEAN 1
+    #define GET_NATIVE_WINDOW(aWidget) ((EGLNativeWindowType)aWidget->GetNativeData(NS_NATIVE_SHAREABLE_WINDOW))
+#else
+    #define GET_NATIVE_WINDOW(aWidget) ((EGLNativeWindowType)aWidget->GetNativeData(NS_NATIVE_WINDOW))
 #endif
 
-#include <windows.h>
+#if defined(XP_UNIX)
+    #ifdef MOZ_WIDGET_GONK
+        #include "libdisplay/GonkDisplay.h"
+        #include "nsWindow.h"
+        #include "nsScreenManagerGonk.h"
+    #endif
 
-// a little helper
-class AutoDestroyHWND {
-public:
-    AutoDestroyHWND(HWND aWnd = nullptr)
-        : mWnd(aWnd)
-    {
-    }
+    #ifdef ANDROID
+        /* from widget */
+        #ifdef MOZ_WIDGET_ANDROID
+            #include "AndroidBridge.h"
+        #endif
+
+        #include <android/log.h>
+        #define LOG(args...)  __android_log_print(ANDROID_LOG_INFO, "Gonk" , ## args)
 
-    ~AutoDestroyHWND() {
-        if (mWnd) {
-            ::DestroyWindow(mWnd);
-        }
-    }
+        #ifdef MOZ_WIDGET_GONK
+            #include "cutils/properties.h"
+            #include <ui/GraphicBuffer.h>
+
+            using namespace android;
+        #endif
+    #endif
 
-    operator HWND() {
-        return mWnd;
-    }
+    #define GLES2_LIB "libGLESv2.so"
+    #define GLES2_LIB2 "libGLESv2.so.2"
+
+#elif defined(XP_WIN)
+    #include "nsIFile.h"
+
+    #define GLES2_LIB "libGLESv2.dll"
+
+    #ifndef WIN32_LEAN_AND_MEAN
+        #define WIN32_LEAN_AND_MEAN 1
+    #endif
 
-    HWND forget() {
-        HWND w = mWnd;
-        mWnd = nullptr;
-        return w;
-    }
+    #include <windows.h>
 
-    HWND operator=(HWND aWnd) {
-        if (mWnd && mWnd != aWnd) {
-            ::DestroyWindow(mWnd);
+    // a little helper
+    class AutoDestroyHWND {
+    public:
+        AutoDestroyHWND(HWND aWnd = nullptr)
+            : mWnd(aWnd)
+        {
+        }
+
+        ~AutoDestroyHWND() {
+            if (mWnd) {
+                ::DestroyWindow(mWnd);
+            }
+        }
+
+        operator HWND() {
+            return mWnd;
         }
-        mWnd = aWnd;
-        return mWnd;
-    }
+
+        HWND forget() {
+            HWND w = mWnd;
+            mWnd = nullptr;
+            return w;
+        }
 
-    HWND mWnd;
-};
+        HWND operator=(HWND aWnd) {
+            if (mWnd && mWnd != aWnd) {
+                ::DestroyWindow(mWnd);
+            }
+            mWnd = aWnd;
+            return mWnd;
+        }
 
+        HWND mWnd;
+    };
 #else
-
-#error "Platform not recognized"
-
+    #error "Platform not recognized"
 #endif
 
-#include "mozilla/Preferences.h"
-#include "gfxUtils.h"
+#include "gfxASurface.h"
+#include "gfxCrashReporterUtils.h"
 #include "gfxFailure.h"
-#include "gfxASurface.h"
 #include "gfxPlatform.h"
+#include "gfxUtils.h"
+#include "GLBlitHelper.h"
+#include "GLContextEGL.h"
 #include "GLContextProvider.h"
 #include "GLLibraryEGL.h"
-#include "TextureImageEGL.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Preferences.h"
 #include "nsDebug.h"
-#include "nsThreadUtils.h"
-
 #include "nsIWidget.h"
-
-#include "gfxCrashReporterUtils.h"
-
+#include "nsThreadUtils.h"
 #include "ScopedGLHelpers.h"
-#include "GLBlitHelper.h"
+#include "TextureImageEGL.h"
 
 using namespace mozilla::gfx;
 
 namespace mozilla {
 namespace gl {
 
 #define ADD_ATTR_2(_array, _k, _v) do {         \
     (_array).AppendElement(_k);                 \
@@ -185,43 +177,41 @@ DestroySurface(EGLSurface oldSurface) {
                                  EGL_NO_SURFACE, EGL_NO_SURFACE,
                                  EGL_NO_CONTEXT);
         sEGLLibrary.fDestroySurface(EGL_DISPLAY(), oldSurface);
     }
 }
 
 static EGLSurface
 CreateSurfaceForWindow(nsIWidget* widget, const EGLConfig& config) {
-    EGLSurface newSurface = EGL_NO_SURFACE;
+    EGLSurface newSurface = nullptr;
 
-    #ifdef MOZ_WIDGET_ANDROID
+#ifdef MOZ_WIDGET_ANDROID
         mozilla::AndroidBridge::Bridge()->RegisterCompositor();
         newSurface = mozilla::AndroidBridge::Bridge()->CreateEGLSurfaceForCompositor();
-        if (newSurface == EGL_NO_SURFACE) {
-            return EGL_NO_SURFACE;
-        }
-    #else
+#else
         MOZ_ASSERT(widget != nullptr);
-        newSurface = sEGLLibrary.fCreateWindowSurface(EGL_DISPLAY(), config, GET_NATIVE_WINDOW(widget), 0);
-    #endif
+        newSurface = sEGLLibrary.fCreateWindowSurface(EGL_DISPLAY(), config,
+                                                      GET_NATIVE_WINDOW(widget), 0);
+#endif
     return newSurface;
 }
 
 GLContextEGL::GLContextEGL(
                   const SurfaceCaps& caps,
                   GLContext* shareContext,
                   bool isOffscreen,
                   EGLConfig config,
                   EGLSurface surface,
                   EGLContext context)
     : GLContext(caps, shareContext, isOffscreen)
     , mConfig(config)
     , mSurface(surface)
+    , mContext(context)
     , mSurfaceOverride(EGL_NO_SURFACE)
-    , mContext(context)
     , mThebesSurface(nullptr)
     , mBound(false)
     , mIsPBuffer(false)
     , mIsDoubleBuffered(false)
     , mCanBindToTexture(false)
     , mShareWithEGLImage(false)
     , mOwnsContext(true)
 {
@@ -420,17 +410,17 @@ GLContextEGL::RenewSurface() {
     // pass again to CreateSurfaceForWindow below.
     // The reason why Android doesn't need this is that it delegates EGLSurface creation to
     // Java code which is the only thing that knows about our actual widget.
 #endif
     // unconditionally release the surface and create a new one. Don't try to optimize this away.
     // If we get here, then by definition we know that we want to get a new surface.
     ReleaseSurface();
     mSurface = mozilla::gl::CreateSurfaceForWindow(nullptr, mConfig); // the nullptr here is where we assume Android.
-    if (mSurface == EGL_NO_SURFACE) {
+    if (!mSurface) {
         return false;
     }
     return MakeCurrent(true);
 }
 
 void
 GLContextEGL::ReleaseSurface() {
     if (mOwnsContext) {
@@ -485,16 +475,20 @@ GLContextEGL::CreateSurfaceForWindow(nsI
 
     EGLConfig config;
     if (!CreateConfig(&config, aWidget)) {
         MOZ_CRASH("Failed to create EGLConfig!\n");
         return nullptr;
     }
 
     EGLSurface surface = mozilla::gl::CreateSurfaceForWindow(aWidget, config);
+    if (!surface) {
+        MOZ_CRASH("Failed to create EGLSurface for window!\n");
+        return nullptr;
+    }
     return surface;
 }
 
 /* static */ void
 GLContextEGL::DestroySurface(EGLSurface aSurface)
 {
     if (aSurface != EGL_NO_SURFACE) {
         sEGLLibrary.fDestroySurface(EGL_DISPLAY(), aSurface);
@@ -775,18 +769,17 @@ GLContextProviderEGL::CreateForWindow(ns
 
     EGLConfig config;
     if (!CreateConfig(&config, aWidget)) {
         MOZ_CRASH("Failed to create EGLConfig!\n");
         return nullptr;
     }
 
     EGLSurface surface = mozilla::gl::CreateSurfaceForWindow(aWidget, config);
-
-    if (surface == EGL_NO_SURFACE) {
+    if (!surface) {
         MOZ_CRASH("Failed to create EGLSurface!\n");
         return nullptr;
     }
 
     SurfaceCaps caps = SurfaceCaps::Any();
     nsRefPtr<GLContextEGL> glContext =
         GLContextEGL::CreateGLContext(caps,
                                       nullptr, false,
@@ -834,70 +827,154 @@ GLContextProviderEGL::DestroyEGLSurface(
     if (!sEGLLibrary.EnsureInitialized()) {
         MOZ_CRASH("Failed to load EGL library!\n");
     }
 
     sEGLLibrary.fDestroySurface(EGL_DISPLAY(), surface);
 }
 #endif // defined(ANDROID)
 
-already_AddRefed<GLContextEGL>
-GLContextEGL::CreateEGLPBufferOffscreenContext(const mozilla::gfx::IntSize& size)
+static void
+FillContextAttribs(bool alpha, bool depth, bool stencil, bool bpp16,
+                   nsTArray<EGLint>* out)
 {
-    EGLConfig config;
-    EGLSurface surface;
+    out->AppendElement(LOCAL_EGL_SURFACE_TYPE);
+    out->AppendElement(LOCAL_EGL_PBUFFER_BIT);
+
+    out->AppendElement(LOCAL_EGL_RENDERABLE_TYPE);
+    out->AppendElement(LOCAL_EGL_OPENGL_ES2_BIT);
+
+    out->AppendElement(LOCAL_EGL_RED_SIZE);
+    if (bpp16) {
+        out->AppendElement(alpha ? 4 : 5);
+    } else {
+        out->AppendElement(8);
+    }
+
+    out->AppendElement(LOCAL_EGL_GREEN_SIZE);
+    if (bpp16) {
+        out->AppendElement(alpha ? 4 : 6);
+    } else {
+        out->AppendElement(8);
+    }
+
+    out->AppendElement(LOCAL_EGL_BLUE_SIZE);
+    if (bpp16) {
+        out->AppendElement(alpha ? 4 : 5);
+    } else {
+        out->AppendElement(8);
+    }
+
+    out->AppendElement(LOCAL_EGL_ALPHA_SIZE);
+    if (alpha) {
+        out->AppendElement(bpp16 ? 4 : 8);
+    } else {
+        out->AppendElement(0);
+    }
 
-    const EGLint numConfigs = 1; // We only need one.
-    EGLConfig configs[numConfigs];
+    out->AppendElement(LOCAL_EGL_DEPTH_SIZE);
+    out->AppendElement(depth ? 16 : 0);
+
+    out->AppendElement(LOCAL_EGL_STENCIL_SIZE);
+    out->AppendElement(stencil ? 8 : 0);
+
+    // EGL_ATTRIBS_LIST_SAFE_TERMINATION_WORKING_AROUND_BUGS
+    out->AppendElement(LOCAL_EGL_NONE);
+    out->AppendElement(0);
+
+    out->AppendElement(0);
+    out->AppendElement(0);
+}
+
+static GLint
+GetAttrib(GLLibraryEGL* egl, EGLConfig config, EGLint attrib)
+{
+    EGLint bits = 0;
+    egl->fGetConfigAttrib(egl->Display(), config, attrib, &bits);
+    MOZ_ASSERT(egl->fGetError() == LOCAL_EGL_SUCCESS);
+
+    return bits;
+}
+
+static EGLConfig
+ChooseConfig(GLLibraryEGL* egl, const SurfaceCaps& minCaps,
+             SurfaceCaps* const out_configCaps)
+{
+    nsTArray<EGLint> configAttribList;
+    FillContextAttribs(minCaps.alpha, minCaps.depth, minCaps.stencil, minCaps.bpp16,
+                       &configAttribList);
+
+    const EGLint* configAttribs = configAttribList.Elements();
+
+    // We're guaranteed to get at least minCaps, and the sorting dictated by the spec for
+    // eglChooseConfig reasonably assures that a reasonable 'best' config is on top.
+    const EGLint kMaxConfigs = 1;
+    EGLConfig configs[kMaxConfigs];
     EGLint foundConfigs = 0;
-    if (!sEGLLibrary.fChooseConfig(EGL_DISPLAY(),
-                                   kEGLConfigAttribsOffscreenPBuffer,
-                                   configs, numConfigs,
-                                   &foundConfigs)
+    if (!egl->fChooseConfig(egl->Display(), configAttribs, configs, kMaxConfigs,
+                            &foundConfigs)
         || foundConfigs == 0)
     {
-        NS_WARNING("No EGL Config for minimal PBuffer!");
+        return EGL_NO_CONFIG;
+    }
+
+    EGLConfig config = configs[0];
+
+    *out_configCaps = minCaps; // Pick up any preserve, etc.
+    out_configCaps->color = true;
+    out_configCaps->alpha   = bool(GetAttrib(egl, config, LOCAL_EGL_ALPHA_SIZE));
+    out_configCaps->depth   = bool(GetAttrib(egl, config, LOCAL_EGL_DEPTH_SIZE));
+    out_configCaps->stencil = bool(GetAttrib(egl, config, LOCAL_EGL_STENCIL_SIZE));
+    out_configCaps->bpp16 = (GetAttrib(egl, config, LOCAL_EGL_RED_SIZE) < 8);
+
+    return config;
+}
+
+/*static*/ already_AddRefed<GLContextEGL>
+GLContextEGL::CreateEGLPBufferOffscreenContext(const mozilla::gfx::IntSize& size,
+                                               const SurfaceCaps& minCaps)
+{
+    SurfaceCaps configCaps;
+    EGLConfig config = ChooseConfig(&sEGLLibrary, minCaps, &configCaps);
+    if (config == EGL_NO_CONFIG) {
+        NS_WARNING("Failed to find a compatible config.");
         return nullptr;
     }
 
-    // We absolutely don't care, so just pick the first one.
-    config = configs[0];
     if (GLContext::ShouldSpew())
         sEGLLibrary.DumpEGLConfig(config);
 
     mozilla::gfx::IntSize pbSize(size);
-    surface = GLContextEGL::CreatePBufferSurfaceTryingPowerOfTwo(config,
-                                                                 LOCAL_EGL_NONE,
-                                                                 pbSize);
+    EGLSurface surface = GLContextEGL::CreatePBufferSurfaceTryingPowerOfTwo(config,
+                                                                            LOCAL_EGL_NONE,
+                                                                            pbSize);
     if (!surface) {
         NS_WARNING("Failed to create PBuffer for context!");
         return nullptr;
     }
 
-    SurfaceCaps dummyCaps = SurfaceCaps::Any();
-    nsRefPtr<GLContextEGL> glContext =
-        GLContextEGL::CreateGLContext(dummyCaps,
-                                      nullptr, true,
-                                      config, surface);
-    if (!glContext) {
+
+    RefPtr<GLContextEGL> gl = GLContextEGL::CreateGLContext(configCaps, nullptr, true,
+                                                            config, surface);
+    if (!gl) {
         NS_WARNING("Failed to create GLContext from PBuffer");
-        sEGLLibrary.fDestroySurface(EGL_DISPLAY(), surface);
+        sEGLLibrary.fDestroySurface(sEGLLibrary.Display(), surface);
         return nullptr;
     }
 
-    if (!glContext->Init()) {
+    if (!gl->Init()) {
         NS_WARNING("Failed to initialize GLContext!");
         // GLContextEGL::dtor will destroy |surface| for us.
         return nullptr;
     }
 
-    return glContext.forget();
+    return gl.forget();
 }
 
-already_AddRefed<GLContextEGL>
+/*static*/ already_AddRefed<GLContextEGL>
 GLContextEGL::CreateEGLPixmapOffscreenContext(const mozilla::gfx::IntSize& size)
 {
     gfxASurface *thebesSurface = nullptr;
     EGLNativePixmapType pixmap = 0;
 
     if (!pixmap) {
         return nullptr;
     }
@@ -927,59 +1004,87 @@ GLContextEGL::CreateEGLPixmapOffscreenCo
         return nullptr;
     }
 
     glContext->HoldSurface(thebesSurface);
 
     return glContext.forget();
 }
 
-already_AddRefed<GLContext>
+/*static*/ already_AddRefed<GLContext>
 GLContextProviderEGL::CreateHeadless(CreateContextFlags flags)
 {
-    if (!sEGLLibrary.EnsureInitialized(bool(flags & CreateContextFlags::FORCE_ENABLE_HARDWARE))) {
+    bool forceEnableHardware = bool(flags & CreateContextFlags::FORCE_ENABLE_HARDWARE);
+    if (!sEGLLibrary.EnsureInitialized(forceEnableHardware))
         return nullptr;
-    }
 
     mozilla::gfx::IntSize dummySize = mozilla::gfx::IntSize(16, 16);
-    nsRefPtr<GLContext> glContext;
-    glContext = GLContextEGL::CreateEGLPBufferOffscreenContext(dummySize);
-    if (!glContext)
-        return nullptr;
-
-    return glContext.forget();
+    SurfaceCaps dummyCaps = SurfaceCaps::Any();
+    return GLContextEGL::CreateEGLPBufferOffscreenContext(dummySize, dummyCaps);
 }
 
 // Under EGL, on Android, pbuffers are supported fine, though
 // often without the ability to texture from them directly.
-already_AddRefed<GLContext>
+/*static*/ already_AddRefed<GLContext>
 GLContextProviderEGL::CreateOffscreen(const mozilla::gfx::IntSize& size,
-                                      const SurfaceCaps& caps,
+                                      const SurfaceCaps& minCaps,
                                       CreateContextFlags flags)
 {
-    nsRefPtr<GLContext> glContext = CreateHeadless(flags);
-    if (!glContext)
+    bool forceEnableHardware = bool(flags & CreateContextFlags::FORCE_ENABLE_HARDWARE);
+    if (!sEGLLibrary.EnsureInitialized(forceEnableHardware))
         return nullptr;
 
-    if (!glContext->InitOffscreen(size, caps))
+    bool canOffscreenUseHeadless = true;
+    if (sEGLLibrary.IsANGLE()) {
+        // ANGLE needs to use PBuffers.
+        canOffscreenUseHeadless = false;
+    }
+
+    RefPtr<GLContext> gl;
+    SurfaceCaps offscreenCaps = minCaps;
+
+    if (canOffscreenUseHeadless) {
+        gl = CreateHeadless(flags);
+        if (!gl)
+            return nullptr;
+    } else {
+        SurfaceCaps minBackbufferCaps = minCaps;
+        if (minCaps.antialias) {
+            minBackbufferCaps.antialias = false;
+            minBackbufferCaps.depth = false;
+            minBackbufferCaps.stencil = false;
+        }
+
+        gl = GLContextEGL::CreateEGLPBufferOffscreenContext(size, minBackbufferCaps);
+        if (!gl)
+            return nullptr;
+
+        offscreenCaps = gl->Caps();
+        if (minCaps.antialias) {
+            offscreenCaps.depth = minCaps.depth;
+            offscreenCaps.stencil = minCaps.stencil;
+        }
+    }
+
+    if (!gl->InitOffscreen(size, offscreenCaps))
         return nullptr;
 
-    return glContext.forget();
+    return gl.forget();
 }
 
 // Don't want a global context on Android as 1) share groups across 2 threads fail on many Tegra drivers (bug 759225)
 // and 2) some mobile devices have a very strict limit on global number of GL contexts (bug 754257)
 // and 3) each EGL context eats 750k on B2G (bug 813783)
-GLContext*
+/*static*/ GLContext*
 GLContextProviderEGL::GetGlobalContext()
 {
     return nullptr;
 }
 
-void
+/*static*/ void
 GLContextProviderEGL::Shutdown()
 {
 }
 
 } /* namespace gl */
 } /* namespace mozilla */
 
 #undef EGL_ATTRIBS_LIST_SAFE_TERMINATION_WORKING_AROUND_BUGS

--- a/gfx/gl/GLContextProviderGLX.cpp
+++ b/gfx/gl/GLContextProviderGLX.cpp
@@ -1125,159 +1125,167 @@ GLContextProviderGLX::CreateForWindow(ns
                                                                      display,
                                                                      window,
                                                                      cfgs[matchIndex],
                                                                      false);
 
     return glContext.forget();
 }
 
-static already_AddRefed<GLContextGLX>
-CreateOffscreenPixmapContext(const IntSize& size)
+static bool
+ChooseConfig(GLXLibrary* glx, Display* display, int screen, const SurfaceCaps& minCaps,
+             ScopedXFree<GLXFBConfig>* const out_scopedConfigArr,
+             GLXFBConfig* const out_config, int* const out_visid)
 {
-    GLXLibrary& glx = sGLXLibrary;
-    if (!glx.EnsureInitialized()) {
-        return nullptr;
-    }
+    ScopedXFree<GLXFBConfig>& scopedConfigArr = *out_scopedConfigArr;
 
-    Display *display = DefaultXDisplay();
-    int xscreen = DefaultScreen(display);
+    if (minCaps.antialias)
+        return false;
 
     int attribs[] = {
         LOCAL_GLX_DRAWABLE_TYPE, LOCAL_GLX_PIXMAP_BIT,
         LOCAL_GLX_X_RENDERABLE, True,
+        LOCAL_GLX_RED_SIZE, 8,
+        LOCAL_GLX_GREEN_SIZE, 8,
+        LOCAL_GLX_BLUE_SIZE, 8,
+        LOCAL_GLX_ALPHA_SIZE, minCaps.alpha ? 8 : 0,
+        LOCAL_GLX_DEPTH_SIZE, minCaps.depth ? 16 : 0,
+        LOCAL_GLX_STENCIL_SIZE, minCaps.stencil ? 8 : 0,
         0
     };
+
     int numConfigs = 0;
+    scopedConfigArr = glx->xChooseFBConfig(display, screen, attribs, &numConfigs);
+    if (!scopedConfigArr || !numConfigs)
+        return false;
 
-    ScopedXFree<GLXFBConfig> cfgs;
-    cfgs = glx.xChooseFBConfig(display,
-                               xscreen,
-                               attribs,
-                               &numConfigs);
-    if (!cfgs) {
-        return nullptr;
-    }
+    // Issues with glxChooseFBConfig selection and sorting:
+    // * ALPHA_SIZE is sorted as 'largest total RGBA bits first'. If we don't request
+    //   alpha bits, we'll probably get RGBA anyways, since 32 is more than 24.
+    // * DEPTH_SIZE is sorted largest first, including for `0` inputs.
+    // * STENCIL_SIZE is smallest first, but it might return `8` even though we ask for
+    //   `0`.
 
-    MOZ_ASSERT(numConfigs > 0,
-               "glXChooseFBConfig() failed to match our requested format and "
-               "violated its spec!");
-
-    int visid = None;
-    int chosenIndex = 0;
+    // For now, we don't care about these. We *will* care when we do XPixmap sharing.
 
     for (int i = 0; i < numConfigs; ++i) {
-        int dtype;
+        GLXFBConfig curConfig = scopedConfigArr[i];
 
-        if (glx.xGetFBConfigAttrib(display, cfgs[i], LOCAL_GLX_DRAWABLE_TYPE, &dtype) != Success
-            || !(dtype & LOCAL_GLX_PIXMAP_BIT))
-        {
-            continue;
-        }
-        if (glx.xGetFBConfigAttrib(display, cfgs[i], LOCAL_GLX_VISUAL_ID, &visid) != Success
-            || visid == 0)
+        int visid;
+        if (glx->xGetFBConfigAttrib(display, curConfig, LOCAL_GLX_VISUAL_ID, &visid)
+            != Success)
         {
             continue;
         }
 
-        chosenIndex = i;
-        break;
+        if (!visid)
+            continue;
+
+        *out_config = curConfig;
+        *out_visid = visid;
+        return true;
     }
 
-    if (!visid) {
-        NS_WARNING("glXChooseFBConfig() didn't give us any configs with visuals!");
+    return false;
+}
+
+static already_AddRefed<GLContextGLX>
+CreateOffscreenPixmapContext(const IntSize& size, const SurfaceCaps& minCaps)
+{
+    GLXLibrary* glx = &sGLXLibrary;
+    if (!glx->EnsureInitialized())
+        return nullptr;
+
+    Display* display = DefaultXDisplay();
+    int screen = DefaultScreen(display);
+
+    ScopedXFree<GLXFBConfig> scopedConfigArr;
+    GLXFBConfig config;
+    int visid;
+    if (!ChooseConfig(glx, display, screen, minCaps, &scopedConfigArr, &config, &visid)) {
+        NS_WARNING("Failed to find a compatible config.");
         return nullptr;
     }
 
-    Visual *visual;
+    Visual* visual;
     int depth;
     FindVisualAndDepth(display, visid, &visual, &depth);
-    ScopedXErrorHandler xErrorHandler;
-    GLXPixmap glxpixmap = 0;
-    bool error = false;
 
-    IntSize dummySize(16, 16);
-    nsRefPtr<gfxXlibSurface> xsurface = gfxXlibSurface::Create(DefaultScreenOfDisplay(display),
-                                                               visual,
-                                                               dummySize);
-    if (xsurface->CairoStatus() != 0) {
+    ScopedXErrorHandler xErrorHandler;
+    bool error = false;
+    // Must be declared before goto:
+    Drawable drawable;
+    GLXPixmap pixmap;
+
+    gfx::IntSize dummySize(16, 16);
+    RefPtr<gfxXlibSurface> surface = gfxXlibSurface::Create(DefaultScreenOfDisplay(display),
+                                                            visual,
+                                                            dummySize);
+    if (surface->CairoStatus() != 0) {
         error = true;
         goto DONE_CREATING_PIXMAP;
     }
 
     // Handle slightly different signature between glXCreatePixmap and
     // its pre-GLX-1.3 extension equivalent (though given the ABI, we
     // might not need to).
-    if (glx.GLXVersionCheck(1, 3)) {
-        glxpixmap = glx.xCreatePixmap(display,
-                                          cfgs[chosenIndex],
-                                          xsurface->XDrawable(),
-                                          nullptr);
+    drawable = surface->XDrawable();
+    if (glx->GLXVersionCheck(1, 3)) {
+        pixmap = glx->xCreatePixmap(display, config, drawable, nullptr);
     } else {
-        glxpixmap = glx.xCreateGLXPixmapWithConfig(display,
-                                                       cfgs[chosenIndex],
-                                                       xsurface->
-                                                       XDrawable());
+        pixmap = glx->xCreateGLXPixmapWithConfig(display, config, drawable);
     }
-    if (glxpixmap == 0) {
+
+    if (pixmap == 0) {
         error = true;
     }
 
 DONE_CREATING_PIXMAP:
 
-    nsRefPtr<GLContextGLX> glContext;
     bool serverError = xErrorHandler.SyncAndGetError(display);
-
-    if (!error && // earlier recorded error
-        !serverError)
-    {
-        // We might have an alpha channel, but it doesn't matter.
-        SurfaceCaps dummyCaps = SurfaceCaps::Any();
-        GLContextGLX* shareContext = GetGlobalContextGLX();
+    if (error || serverError)
+        return nullptr;
 
-        glContext = GLContextGLX::CreateGLContext(dummyCaps,
-                                                  shareContext,
-                                                  true,
-                                                  display,
-                                                  glxpixmap,
-                                                  cfgs[chosenIndex],
-                                                  true,
-                                                  xsurface);
-    }
-
-    return glContext.forget();
+    GLContextGLX* shareContext = GetGlobalContextGLX();
+    return GLContextGLX::CreateGLContext(minCaps, shareContext, true, display, pixmap,
+                                         config, true, surface);
 }
 
-already_AddRefed<GLContext>
+/*static*/ already_AddRefed<GLContext>
 GLContextProviderGLX::CreateHeadless(CreateContextFlags)
 {
     IntSize dummySize = IntSize(16, 16);
-    nsRefPtr<GLContext> glContext = CreateOffscreenPixmapContext(dummySize);
-    if (!glContext)
-        return nullptr;
-
-    return glContext.forget();
+    SurfaceCaps dummyCaps = SurfaceCaps::Any();
+    return CreateOffscreenPixmapContext(dummySize, dummyCaps);
 }
 
-already_AddRefed<GLContext>
+/*static*/ already_AddRefed<GLContext>
 GLContextProviderGLX::CreateOffscreen(const IntSize& size,
-                                      const SurfaceCaps& caps,
+                                      const SurfaceCaps& minCaps,
                                       CreateContextFlags flags)
 {
-    nsRefPtr<GLContext> glContext = CreateHeadless(flags);
-    if (!glContext)
+    SurfaceCaps minBackbufferCaps = minCaps;
+    if (minCaps.antialias) {
+        minBackbufferCaps.antialias = false;
+        minBackbufferCaps.depth = false;
+        minBackbufferCaps.stencil = false;
+    }
+
+    RefPtr<GLContext> gl;
+    gl = CreateOffscreenPixmapContext(size, minBackbufferCaps);
+    if (!gl)
         return nullptr;
 
-    if (!glContext->InitOffscreen(size, caps))
+    if (!gl->InitOffscreen(size, minCaps))
         return nullptr;
 
-    return glContext.forget();
+    return gl.forget();
 }
 
-GLContext*
+/*static*/ GLContext*
 GLContextProviderGLX::GetGlobalContext()
 {
     static bool checkedContextSharing = false;
     static bool useContextSharing = false;
 
     if (!checkedContextSharing) {
         useContextSharing = getenv("MOZ_DISABLE_CONTEXT_SHARING_GLX") == 0;
         checkedContextSharing = true;
@@ -1288,27 +1296,29 @@ GLContextProviderGLX::GetGlobalContext()
         return nullptr;
     }
 
     static bool triedToCreateContext = false;
     if (!triedToCreateContext && !gGlobalContext) {
         triedToCreateContext = true;
 
         IntSize dummySize = IntSize(16, 16);
+        SurfaceCaps dummyCaps = SurfaceCaps::Any();
         // StaticPtr doesn't support assignments from already_AddRefed,
         // so use a temporary nsRefPtr to make the reference counting
         // fall out correctly.
-        nsRefPtr<GLContext> holder = CreateOffscreenPixmapContext(dummySize);
+        RefPtr<GLContext> holder;
+        holder = CreateOffscreenPixmapContext(dummySize, dummyCaps);
         gGlobalContext = holder;
     }
 
     return gGlobalContext;
 }
 
-void
+/*static*/ void
 GLContextProviderGLX::Shutdown()
 {
     gGlobalContext = nullptr;
 }
 
 } /* namespace gl */
 } /* namespace mozilla */
 

--- a/gfx/gl/GLContextProviderImpl.h
+++ b/gfx/gl/GLContextProviderImpl.h
@@ -49,26 +49,28 @@ public:
      *
      * The offscreen context returned by this method will always have
      * the ability to be rendered into a context created by a window.
      * It might or might not share resources with the global context;
      * query GetSharedContext() for a non-null result to check.  If
      * resource sharing can be avoided on the target platform, it will
      * be, in order to isolate the offscreen context.
      *
-     * @param size The initial size of this offscreen context.
-     * @param caps The SurfaceCaps for this offscreen context.
-     * @param flags The set of CreateContextFlags to be used for this
-     *              offscreen context.
+     * @param size    The initial size of this offscreen context.
+     * @param minCaps The required SurfaceCaps for this offscreen context. The resulting
+     *                context *may* have more/better caps than requested, but it cannot
+     *                have fewer/worse caps than requested.
+     * @param flags   The set of CreateContextFlags to be used for this
+     *                offscreen context.
      *
      * @return Context to use for offscreen rendering
      */
     static already_AddRefed<GLContext>
     CreateOffscreen(const mozilla::gfx::IntSize& size,
-                    const SurfaceCaps& caps,
+                    const SurfaceCaps& minCaps,
                     CreateContextFlags flags);
 
     // Just create a context. We'll add offscreen stuff ourselves.
     static already_AddRefed<GLContext>
     CreateHeadless(CreateContextFlags flags);
 
     /**
      * Create wrapping Gecko GLContext for external gl context.

--- a/gfx/gl/GLContextProviderWGL.cpp
+++ b/gfx/gl/GLContextProviderWGL.cpp
@@ -601,17 +601,17 @@ CreateWindowOffscreenContext()
     SurfaceCaps caps = SurfaceCaps::ForRGBA();
     nsRefPtr<GLContextWGL> glContext = new GLContextWGL(caps,
                                                         shareContext, true,
                                                         dc, context, win);
 
     return glContext.forget();
 }
 
-already_AddRefed<GLContext>
+/*static*/ already_AddRefed<GLContext>
 GLContextProviderWGL::CreateHeadless(CreateContextFlags)
 {
     if (!sWGLLib.EnsureInitialized()) {
         return nullptr;
     }
 
     nsRefPtr<GLContextWGL> glContext;
 
@@ -634,34 +634,34 @@ GLContextProviderWGL::CreateHeadless(Cre
     {
         return nullptr;
     }
 
     nsRefPtr<GLContext> retGL = glContext.get();
     return retGL.forget();
 }
 
-already_AddRefed<GLContext>
+/*static*/ already_AddRefed<GLContext>
 GLContextProviderWGL::CreateOffscreen(const IntSize& size,
-                                      const SurfaceCaps& caps,
+                                      const SurfaceCaps& minCaps,
                                       CreateContextFlags flags)
 {
-    nsRefPtr<GLContext> glContext = CreateHeadless(flags);
-    if (!glContext)
+    RefPtr<GLContext> gl = CreateHeadless(flags);
+    if (!gl)
         return nullptr;
 
-    if (!glContext->InitOffscreen(size, caps))
+    if (!gl->InitOffscreen(size, minCaps))
         return nullptr;
 
-    return glContext.forget();
+    return gl.forget();
 }
 
 static nsRefPtr<GLContextWGL> gGlobalContext;
 
-GLContext *
+/*static*/ GLContext*
 GLContextProviderWGL::GetGlobalContext()
 {
     if (!sWGLLib.EnsureInitialized()) {
         return nullptr;
     }
 
     static bool triedToCreateContext = false;
 
@@ -679,16 +679,16 @@ GLContextProviderWGL::GetGlobalContext()
             gGlobalContext = nullptr;
             return nullptr;
         }
     }
 
     return static_cast<GLContext*>(gGlobalContext);
 }
 
-void
+/*static*/ void
 GLContextProviderWGL::Shutdown()
 {
     gGlobalContext = nullptr;
 }
 
 } /* namespace gl */
 } /* namespace mozilla */

--- a/gfx/gl/GLContextTypes.h
+++ b/gfx/gl/GLContextTypes.h
@@ -2,16 +2,17 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef GLCONTEXT_TYPES_H_
 #define GLCONTEXT_TYPES_H_
 
 #include "GLTypes.h"
+#include "mozilla/TypedEnumBits.h"
 
 namespace mozilla {
 namespace gl {
 
 class GLContext;
 
 enum class GLContextType {
     Unknown,
@@ -38,12 +39,22 @@ struct GLFormats
 
     GLenum depthStencil;
     GLenum depth;
     GLenum stencil;
 
     GLsizei samples;
 };
 
+enum class CreateContextFlags : int8_t {
+    NONE = 0,
+    REQUIRE_COMPAT_PROFILE = 1 << 0,
+    // Force the use of hardware backed GL, don't allow software implementations.
+    FORCE_ENABLE_HARDWARE = 1 << 1,
+    /* Don't force discrete GPU to be used (if applicable) */
+    ALLOW_OFFLINE_RENDERER =  1 << 2,
+};
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(CreateContextFlags)
+
 } /* namespace gl */
 } /* namespace mozilla */
 
 #endif /* GLCONTEXT_TYPES_H_ */

--- a/gfx/gl/GLLibraryEGL.h
+++ b/gfx/gl/GLLibraryEGL.h
@@ -12,50 +12,42 @@
 #include "GLLibraryLoader.h"
 #include "mozilla/ThreadLocal.h"
 #include "nsIFile.h"
 #include "GeckoProfiler.h"
 
 #include <bitset>
 #include <vector>
 
-#if defined(XP_WIN)
-
-#ifndef WIN32_LEAN_AND_MEAN
-#define WIN32_LEAN_AND_MEAN 1
-#endif
+#ifdef XP_WIN
+    #ifndef WIN32_LEAN_AND_MEAN
+        #define WIN32_LEAN_AND_MEAN 1
+    #endif
 
-#include <windows.h>
+    #include <windows.h>
 
-typedef HDC EGLNativeDisplayType;
-typedef HBITMAP EGLNativePixmapType;
-typedef HWND EGLNativeWindowType;
-
-#define GET_NATIVE_WINDOW(aWidget) ((EGLNativeWindowType)aWidget->GetNativeData(NS_NATIVE_WINDOW))
-
+    typedef HDC EGLNativeDisplayType;
+    typedef HBITMAP EGLNativePixmapType;
+    typedef HWND EGLNativeWindowType;
 #else
-typedef void *EGLNativeDisplayType;
-typedef void *EGLNativePixmapType;
-typedef void *EGLNativeWindowType;
+    typedef void* EGLNativeDisplayType;
+    typedef void* EGLNativePixmapType;
+    typedef void* EGLNativeWindowType;
 
-#ifdef ANDROID
-// We only need to explicitly dlopen egltrace
-// on android as we can use LD_PRELOAD or other tricks
-// on other platforms. We look for it in /data/local
-// as that's writeable by all users
-//
-// This should really go in GLLibraryEGL.cpp but we currently reference
-// APITRACE_LIB in GLContextProviderEGL.cpp. Further refactoring
-// will come in subsequent patches on Bug 732865
-#define APITRACE_LIB "/data/local/tmp/egltrace.so"
-
-#ifdef MOZ_WIDGET_ANDROID
-
-#endif // MOZ_WIDGET_ANDROID
-#endif // ANDROID
+    #ifdef ANDROID
+        // We only need to explicitly dlopen egltrace
+        // on android as we can use LD_PRELOAD or other tricks
+        // on other platforms. We look for it in /data/local
+        // as that's writeable by all users
+        //
+        // This should really go in GLLibraryEGL.cpp but we currently reference
+        // APITRACE_LIB in GLContextProviderEGL.cpp. Further refactoring
+        // will come in subsequent patches on Bug 732865
+        #define APITRACE_LIB "/data/local/tmp/egltrace.so"
+    #endif
 #endif
 
 #if defined(MOZ_X11)
 #define EGL_DEFAULT_DISPLAY  ((EGLNativeDisplayType)mozilla::DefaultXDisplay())
 #else
 #define EGL_DEFAULT_DISPLAY  ((EGLNativeDisplayType)0)
 #endif
 

--- a/gfx/gl/GLScreenBuffer.cpp
+++ b/gfx/gl/GLScreenBuffer.cpp
@@ -481,19 +481,26 @@ GLScreenBuffer::Swap(const gfx::IntSize&
         !mDraw)
     {
         auto src  = mFront->Surf();
         auto dest = mBack->Surf();
 
         //uint32_t srcPixel = ReadPixel(src);
         //uint32_t destPixel = ReadPixel(dest);
         //printf_stderr("Before: src: 0x%08x, dest: 0x%08x\n", srcPixel, destPixel);
+#ifdef DEBUG
+        GLContext::LocalErrorScope errorScope(*mGL);
+#endif
 
         SharedSurface::ProdCopy(src, dest, mFactory.get());
 
+#ifdef DEBUG
+        MOZ_ASSERT(!errorScope.GetError());
+#endif
+
         //srcPixel = ReadPixel(src);
         //destPixel = ReadPixel(dest);
         //printf_stderr("After: src: 0x%08x, dest: 0x%08x\n", srcPixel, destPixel);
     }
 
     // XXX: We would prefer to fence earlier on platforms that don't need
     // the full ProducerAcquire/ProducerRelease semantics, so that the fence
     // doesn't include the copy operation. Unfortunately, the current API

--- a/gfx/gl/SharedSurfaceANGLE.cpp
+++ b/gfx/gl/SharedSurfaceANGLE.cpp
@@ -36,27 +36,24 @@ CreatePBufferSurface(GLLibraryEGL* egl,
     EGLint err = egl->fGetError();
     if (err != LOCAL_EGL_SUCCESS)
         return 0;
 
     return surface;
 }
 
 /*static*/ UniquePtr<SharedSurface_ANGLEShareHandle>
-SharedSurface_ANGLEShareHandle::Create(GLContext* gl,
-                                       EGLContext context, EGLConfig config,
+SharedSurface_ANGLEShareHandle::Create(GLContext* gl, EGLConfig config,
                                        const gfx::IntSize& size, bool hasAlpha)
 {
     GLLibraryEGL* egl = &sEGLLibrary;
     MOZ_ASSERT(egl);
     MOZ_ASSERT(egl->IsExtensionSupported(
                GLLibraryEGL::ANGLE_surface_d3d_texture_2d_share_handle));
-
-    if (!context || !config)
-        return nullptr;
+    MOZ_ASSERT(config);
 
     EGLDisplay display = egl->Display();
     EGLSurface pbuffer = CreatePBufferSurface(egl, display, config, size);
     if (!pbuffer)
         return nullptr;
 
     // Declare everything before 'goto's.
     HANDLE shareHandle = nullptr;
@@ -77,44 +74,42 @@ SharedSurface_ANGLEShareHandle::Create(G
 
     GLuint fence = 0;
     if (gl->IsExtensionSupported(GLContext::NV_fence)) {
         gl->MakeCurrent();
         gl->fGenFences(1, &fence);
     }
 
     typedef SharedSurface_ANGLEShareHandle ptrT;
-    UniquePtr<ptrT> ret( new ptrT(gl, egl, size, hasAlpha, context,
-                                  pbuffer, shareHandle, keyedMutex, fence) );
+    UniquePtr<ptrT> ret( new ptrT(gl, egl, size, hasAlpha, pbuffer, shareHandle,
+                                  keyedMutex, fence) );
     return Move(ret);
 }
 
 EGLDisplay
 SharedSurface_ANGLEShareHandle::Display()
 {
     return mEGL->Display();
 }
 
 SharedSurface_ANGLEShareHandle::SharedSurface_ANGLEShareHandle(GLContext* gl,
                                                                GLLibraryEGL* egl,
                                                                const gfx::IntSize& size,
                                                                bool hasAlpha,
-                                                               EGLContext context,
                                                                EGLSurface pbuffer,
                                                                HANDLE shareHandle,
                                                                const RefPtr<IDXGIKeyedMutex>& keyedMutex,
                                                                GLuint fence)
     : SharedSurface(SharedSurfaceType::EGLSurfaceANGLE,
                     AttachmentType::Screen,
                     gl,
                     size,
                     hasAlpha,
                     true)
     , mEGL(egl)
-    , mContext(context)
     , mPBuffer(pbuffer)
     , mShareHandle(shareHandle)
     , mKeyedMutex(keyedMutex)
     , mFence(fence)
 {
 }
 
 
@@ -276,186 +271,42 @@ SharedSurface_ANGLEShareHandle::ToSurfac
     *out_descriptor = layers::SurfaceDescriptorD3D10((WindowsHandle)mShareHandle, format,
                                                      mSize);
     return true;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // Factory
 
-static void
-FillPBufferAttribs_ByBits(nsTArray<EGLint>& aAttrs,
-                          int redBits, int greenBits,
-                          int blueBits, int alphaBits,
-                          int depthBits, int stencilBits)
-{
-    aAttrs.Clear();
-
-#if defined(A1) || defined(A2)
-#error The temp-macro names we want are already defined.
-#endif
-
-#define A1(_x)      do { aAttrs.AppendElement(_x); } while (0)
-#define A2(_x,_y)   do { A1(_x); A1(_y); } while (0)
-
-    A2(LOCAL_EGL_RENDERABLE_TYPE, LOCAL_EGL_OPENGL_ES2_BIT);
-    A2(LOCAL_EGL_SURFACE_TYPE, LOCAL_EGL_PBUFFER_BIT);
-
-    A2(LOCAL_EGL_RED_SIZE, redBits);
-    A2(LOCAL_EGL_GREEN_SIZE, greenBits);
-    A2(LOCAL_EGL_BLUE_SIZE, blueBits);
-    A2(LOCAL_EGL_ALPHA_SIZE, alphaBits);
-
-    A2(LOCAL_EGL_DEPTH_SIZE, depthBits);
-    A2(LOCAL_EGL_STENCIL_SIZE, stencilBits);
-
-    A1(LOCAL_EGL_NONE);
-#undef A1
-#undef A2
-}
-
-static void
-FillPBufferAttribs_BySizes(nsTArray<EGLint>& attribs,
-                           bool bpp16, bool hasAlpha,
-                           int depthBits, int stencilBits)
-{
-    int red = 0;
-    int green = 0;
-    int blue = 0;
-    int alpha = 0;
-
-    if (bpp16) {
-        if (hasAlpha) {
-            red = green = blue = alpha = 4;
-        } else {
-            red = 5;
-            green = 6;
-            blue = 5;
-        }
-    } else {
-        red = green = blue = 8;
-        if (hasAlpha)
-            alpha = 8;
-    }
-
-    FillPBufferAttribs_ByBits(attribs, red, green, blue, alpha, depthBits,
-                              stencilBits);
-}
-
-static bool
-DoesAttribBitsMatchCapBool(GLLibraryEGL* egl, EGLConfig config, EGLint attrib,
-                           bool capBool)
-{
-    EGLint bits = 0;
-    egl->fGetConfigAttrib(egl->Display(), config, attrib, &bits);
-    MOZ_ASSERT(egl->fGetError() == LOCAL_EGL_SUCCESS);
-
-    bool hasBits = !!bits;
-
-    return hasBits == capBool;
-}
-
-static EGLConfig
-ChooseConfig(GLContext* gl, GLLibraryEGL* egl, const SurfaceCaps& caps)
-{
-    MOZ_ASSERT(egl);
-    MOZ_ASSERT(caps.color);
-
-    // We might want 24-bit depth, but we're only (fairly) sure to get 16-bit.
-    int depthBits = caps.depth ? 16 : 0;
-    int stencilBits = caps.stencil ? 8 : 0;
-
-    // Ok, now we have everything.
-    nsTArray<EGLint> attribs(32);
-    FillPBufferAttribs_BySizes(attribs, caps.bpp16, caps.alpha, depthBits,
-                               stencilBits);
-
-    // Time to try to get this config:
-    EGLConfig configs[64];
-    int numConfigs = sizeof(configs)/sizeof(EGLConfig);
-    int foundConfigs = 0;
-
-    if (!egl->fChooseConfig(egl->Display(), attribs.Elements(), configs,
-                            numConfigs, &foundConfigs) ||
-        !foundConfigs)
-    {
-        NS_WARNING("No configs found for the requested formats.");
-        return EGL_NO_CONFIG;
-    }
-
-    // The requests passed to ChooseConfig are treated as minimums. If you ask
-    // for 0 bits of alpha, we might still get 8 bits.
-    EGLConfig config = EGL_NO_CONFIG;
-    for (int i = 0; i < foundConfigs; i++) {
-        EGLConfig cur = configs[i];
-        if (!DoesAttribBitsMatchCapBool(egl, cur, LOCAL_EGL_ALPHA_SIZE,
-                                        caps.alpha) ||
-            !DoesAttribBitsMatchCapBool(egl, cur, LOCAL_EGL_DEPTH_SIZE,
-                                        caps.depth) ||
-            !DoesAttribBitsMatchCapBool(egl, cur, LOCAL_EGL_STENCIL_SIZE,
-                                        caps.stencil))
-        {
-            continue;
-        }
-
-        config = cur;
-        break;
-    }
-
-    if (config == EGL_NO_CONFIG) {
-        NS_WARNING("No acceptable EGLConfig found.");
-        return EGL_NO_CONFIG;
-    }
-
-    if (gl->DebugMode()) {
-        egl->DumpEGLConfig(config);
-    }
-
-    return config;
-}
-
 /*static*/ UniquePtr<SurfaceFactory_ANGLEShareHandle>
 SurfaceFactory_ANGLEShareHandle::Create(GLContext* gl, const SurfaceCaps& caps,
                                         const RefPtr<layers::ISurfaceAllocator>& allocator,
                                         const layers::TextureFlags& flags)
 {
     GLLibraryEGL* egl = &sEGLLibrary;
     if (!egl)
         return nullptr;
 
     auto ext = GLLibraryEGL::ANGLE_surface_d3d_texture_2d_share_handle;
     if (!egl->IsExtensionSupported(ext))
         return nullptr;
 
-    bool success;
-    typedef SurfaceFactory_ANGLEShareHandle ptrT;
-    UniquePtr<ptrT> ret( new ptrT(gl, caps, allocator, flags, egl, &success) );
+    EGLConfig config = GLContextEGL::Cast(gl)->mConfig;
 
-    if (!success)
-        return nullptr;
-
+    typedef SurfaceFactory_ANGLEShareHandle ptrT;
+    UniquePtr<ptrT> ret( new ptrT(gl, caps, allocator, flags, egl, config) );
     return Move(ret);
 }
 
 SurfaceFactory_ANGLEShareHandle::SurfaceFactory_ANGLEShareHandle(GLContext* gl,
                                                                  const SurfaceCaps& caps,
                                                                  const RefPtr<layers::ISurfaceAllocator>& allocator,
                                                                  const layers::TextureFlags& flags,
                                                                  GLLibraryEGL* egl,
-                                                                 bool* const out_success)
+                                                                 EGLConfig config)
     : SurfaceFactory(SharedSurfaceType::EGLSurfaceANGLE, gl, caps, allocator, flags)
     , mProdGL(gl)
     , mEGL(egl)
-{
-    MOZ_ASSERT(out_success);
-    *out_success = false;
-
-    mContext = GLContextEGL::Cast(mProdGL)->GetEGLContext();
-    mConfig = ChooseConfig(mProdGL, mEGL, mReadCaps);
-    if (mConfig == EGL_NO_CONFIG)
-        return;
-
-    MOZ_ASSERT(mConfig && mContext);
-    *out_success = true;
-}
+    , mConfig(config)
+{ }
 
 } /* namespace gl */
 } /* namespace mozilla */

--- a/gfx/gl/SharedSurfaceANGLE.h
+++ b/gfx/gl/SharedSurfaceANGLE.h
@@ -18,45 +18,42 @@ namespace gl {
 class GLContext;
 class GLLibraryEGL;
 
 class SharedSurface_ANGLEShareHandle
     : public SharedSurface
 {
 public:
     static UniquePtr<SharedSurface_ANGLEShareHandle> Create(GLContext* gl,
-                                                            EGLContext context,
                                                             EGLConfig config,
                                                             const gfx::IntSize& size,
                                                             bool hasAlpha);
 
     static SharedSurface_ANGLEShareHandle* Cast(SharedSurface* surf) {
         MOZ_ASSERT(surf->mType == SharedSurfaceType::EGLSurfaceANGLE);
 
         return (SharedSurface_ANGLEShareHandle*)surf;
     }
 
 protected:
     GLLibraryEGL* const mEGL;
-    const EGLContext mContext;
     const EGLSurface mPBuffer;
 public:
     const HANDLE mShareHandle;
 protected:
     RefPtr<IDXGIKeyedMutex> mKeyedMutex;
     RefPtr<IDXGIKeyedMutex> mConsumerKeyedMutex;
     RefPtr<ID3D11Texture2D> mConsumerTexture;
 
     const GLuint mFence;
 
     SharedSurface_ANGLEShareHandle(GLContext* gl,
                                    GLLibraryEGL* egl,
                                    const gfx::IntSize& size,
                                    bool hasAlpha,
-                                   EGLContext context,
                                    EGLSurface pbuffer,
                                    HANDLE shareHandle,
                                    const RefPtr<IDXGIKeyedMutex>& keyedMutex,
                                    GLuint fence);
 
     EGLDisplay Display();
 
 public:
@@ -89,35 +86,32 @@ public:
 
 
 class SurfaceFactory_ANGLEShareHandle
     : public SurfaceFactory
 {
 protected:
     GLContext* const mProdGL;
     GLLibraryEGL* const mEGL;
-    EGLContext mContext;
-    EGLConfig mConfig;
+    const EGLConfig mConfig;
 
 public:
     static UniquePtr<SurfaceFactory_ANGLEShareHandle> Create(GLContext* gl,
                                                              const SurfaceCaps& caps,
                                                              const RefPtr<layers::ISurfaceAllocator>& allocator,
                                                              const layers::TextureFlags& flags);
 
 protected:
     SurfaceFactory_ANGLEShareHandle(GLContext* gl, const SurfaceCaps& caps,
                                     const RefPtr<layers::ISurfaceAllocator>& allocator,
                                     const layers::TextureFlags& flags, GLLibraryEGL* egl,
-                                    bool* const out_success);
+                                    EGLConfig config);
 
     virtual UniquePtr<SharedSurface> CreateShared(const gfx::IntSize& size) override {
         bool hasAlpha = mReadCaps.alpha;
-        return SharedSurface_ANGLEShareHandle::Create(mProdGL,
-                                                      mContext, mConfig,
-                                                      size, hasAlpha);
+        return SharedSurface_ANGLEShareHandle::Create(mProdGL, mConfig, size, hasAlpha);
     }
 };
 
 } /* namespace gfx */
 } /* namespace mozilla */
 
 #endif /* SHARED_SURFACE_ANGLE_H_ */

--- a/gfx/gl/SharedSurfaceEGL.cpp
+++ b/gfx/gl/SharedSurfaceEGL.cpp
@@ -215,17 +215,17 @@ SharedSurface_EGLImage::ToSurfaceDescrip
 
 ////////////////////////////////////////////////////////////////////////
 
 /*static*/ UniquePtr<SurfaceFactory_EGLImage>
 SurfaceFactory_EGLImage::Create(GLContext* prodGL, const SurfaceCaps& caps,
                                 const RefPtr<layers::ISurfaceAllocator>& allocator,
                                 const layers::TextureFlags& flags)
 {
-    EGLContext context = GLContextEGL::Cast(prodGL)->GetEGLContext();
+    EGLContext context = GLContextEGL::Cast(prodGL)->mContext;
 
     typedef SurfaceFactory_EGLImage ptrT;
     UniquePtr<ptrT> ret;
 
     GLLibraryEGL* egl = &sEGLLibrary;
     if (SharedSurface_EGLImage::HasExtensions(egl, prodGL)) {
         ret.reset( new ptrT(prodGL, caps, allocator, flags, context) );
     }

--- a/gfx/gl/moz.build
+++ b/gfx/gl/moz.build
@@ -66,17 +66,17 @@ if CONFIG['MOZ_X11']:
 # Win32 is a special snowflake, for ANGLE
 if CONFIG['MOZ_WIDGET_TOOLKIT'] == 'windows':
     EXPORTS += [
         'GLContextWGL.h',
         'SharedSurfaceANGLE.h', # Needs <windows.h> for `HANDLE`.
         'WGLLibrary.h',
     ]
     UNIFIED_SOURCES += [
-        'GLContextProviderEGL.cpp',
+        'GLContextProviderWGL.cpp',
         'SharedSurfaceANGLE.cpp',
     ]
 if CONFIG['MOZ_ENABLE_SKIA_GPU']:
     EXPORTS += ['SkiaGLGlue.h']
     UNIFIED_SOURCES += [
         'SkiaGLGlue.cpp',
     ]
 
@@ -108,30 +108,27 @@ elif gl_provider == 'GLX':
     # as it includes X11 headers which cause conflicts.
     SOURCES += [
         'GLContextProviderGLX.cpp',
         'SharedSurfaceGLX.cpp'
     ]
     EXPORTS += [
         'SharedSurfaceGLX.h'
     ]
-else:
-    UNIFIED_SOURCES += [
-        'GLContextProvider%s.cpp' % gl_provider,
-    ]
 
 UNIFIED_SOURCES += [
     'AndroidNativeWindow.cpp',
     'AndroidSurfaceTexture.cpp',
     'DecomposeIntoNoRepeatTriangles.cpp',
     'EGLUtils.cpp',
     'GfxTexturesReporter.cpp',
     'GLBlitHelper.cpp',
     'GLContext.cpp',
     'GLContextFeatures.cpp',
+    'GLContextProviderEGL.cpp',
     'GLContextTypes.cpp',
     'GLDebugUtils.cpp',
     'GLLibraryEGL.cpp',
     'GLLibraryLoader.cpp',
     'GLReadTexImageHelper.cpp',
     'GLScreenBuffer.cpp',
     'GLTextureImage.cpp',
     'GLUploadHelpers.cpp',