--- a/gfx/gl/GLConsts.h
+++ b/gfx/gl/GLConsts.h
@@ -5182,16 +5182,18 @@
 #define LOCAL_EGL_CONTEXT_PRIORITY_MEDIUM_IMG                0x3102
 #define LOCAL_EGL_CORE_NATIVE_ENGINE                         0x305B
 #define LOCAL_EGL_COVERAGE_BUFFERS_NV                        0x30E0
 #define LOCAL_EGL_COVERAGE_SAMPLES_NV                        0x30E1
 #define LOCAL_EGL_COVERAGE_SAMPLE_RESOLVE_DEFAULT_NV         0x3132
 #define LOCAL_EGL_COVERAGE_SAMPLE_RESOLVE_NONE_NV            0x3133
 #define LOCAL_EGL_COVERAGE_SAMPLE_RESOLVE_NV                 0x3131
 #define LOCAL_EGL_D3D_TEXTURE_2D_SHARE_HANDLE_ANGLE          0x3200
+#define LOCAL_EGL_D3D11_ELSE_D3D9_DISPLAY_ANGLE              ((EGLNativeDisplayType)-2)
+#define LOCAL_EGL_D3D11_ONLY_DISPLAY_ANGLE                   ((EGLNativeDisplayType)-3)
 #define LOCAL_EGL_DEFAULT_DISPLAY                            ((EGLNativeDisplayType)0)
 #define LOCAL_EGL_DEPTH_ENCODING_NONE_NV                     0
 #define LOCAL_EGL_DEPTH_ENCODING_NONLINEAR_NV                0x30E3
 #define LOCAL_EGL_DEPTH_ENCODING_NV                          0x30E2
 #define LOCAL_EGL_DEPTH_SIZE                                 0x3025
 #define LOCAL_EGL_DISCARD_SAMPLES_ARM                        0x3286
 #define LOCAL_EGL_DISPLAY_SCALING                            10000
 #define LOCAL_EGL_DMA_BUF_PLANE0_FD_EXT                      0x3272

--- a/gfx/gl/GLContext.cpp
+++ b/gfx/gl/GLContext.cpp
@@ -1735,20 +1735,19 @@ GLContext::UpdatePixelFormat()
 #ifdef DEBUG
     const SurfaceCaps& caps = Caps();
     MOZ_ASSERT(!caps.any, "Did you forget to DetermineCaps()?");
 
     MOZ_ASSERT(caps.color == !!format.red);
     MOZ_ASSERT(caps.color == !!format.green);
     MOZ_ASSERT(caps.color == !!format.blue);
 
-    MOZ_ASSERT(caps.alpha == !!format.alpha);
-
     // These we either must have if they're requested, or
     // we can have if they're not.
+    MOZ_ASSERT(caps.alpha == !!format.alpha || !caps.alpha);
     MOZ_ASSERT(caps.depth == !!format.depth || !caps.depth);
     MOZ_ASSERT(caps.stencil == !!format.stencil || !caps.stencil);
 
     MOZ_ASSERT(caps.antialias == (format.samples > 1));
 #endif
     mPixelFormat = new PixelBufferFormat(format);
 }
 

--- a/gfx/gl/GLLibraryEGL.cpp
+++ b/gfx/gl/GLLibraryEGL.cpp
@@ -227,17 +227,39 @@ GLLibraryEGL::EnsureInitialized()
 
     GLLibraryLoader::LoadSymbols(mEGLLibrary, &optionalSymbols[0]);
 
 #if defined(MOZ_WIDGET_GONK) && ANDROID_VERSION >= 18
     MOZ_RELEASE_ASSERT(mSymbols.fQueryStringImplementationANDROID,
                        "Couldn't find eglQueryStringImplementationANDROID");
 #endif
 
-    mEGLDisplay = fGetDisplay(EGL_DEFAULT_DISPLAY);
+    mEGLDisplay = nullptr;
+
+#ifdef XP_WIN
+    // XXX we have no way of knowing if this is ANGLE, or if we're just using
+    // a native EGL on windows.  We don't really do the latter right now, so
+    // let's assume it is ANGLE, and try our special types.
+
+    // D3D11 ANGLE only works with OMTC; there's a bug in the non-OMTC layer
+    // manager, and it's pointless to try to fix it.  We also don't try D3D11
+    // ANGLE if the layer manager is prefering D3D9 (hrm, do we care?)
+    if (gfxPrefs::LayersOffMainThreadCompositionEnabled() &&
+        !gfxPrefs::LayersPreferD3D9())
+    {
+        if (gfxPrefs::WebGLANGLEForceD3D11()) {
+            mEGLDisplay = fGetDisplay(LOCAL_EGL_D3D11_ONLY_DISPLAY_ANGLE);
+        } else if (gfxPrefs::WebGLANGLETryD3D11()) {
+            mEGLDisplay = fGetDisplay(LOCAL_EGL_D3D11_ELSE_D3D9_DISPLAY_ANGLE);
+        }
+    }
+#endif
+
+    if (!mEGLDisplay)
+        mEGLDisplay = fGetDisplay(EGL_DEFAULT_DISPLAY);
     if (!fInitialize(mEGLDisplay, nullptr, nullptr))
         return false;
 
     const char *vendor = (const char*) fQueryString(mEGLDisplay, LOCAL_EGL_VENDOR);
     if (vendor && (strstr(vendor, "TransGaming") != 0 || strstr(vendor, "Google Inc.") != 0)) {
         mIsANGLE = true;
     }
 

--- a/gfx/thebes/gfxPrefs.h
+++ b/gfx/thebes/gfxPrefs.h
@@ -299,16 +299,18 @@ private:
   DECL_GFX_PREF(Live, "layout.event-regions.enabled",          LayoutEventRegionsEnabled, bool, false);
   DECL_GFX_PREF(Once, "layout.paint_rects_separately",         LayoutPaintRectsSeparately, bool, true);
 
   DECL_GFX_PREF(Live, "nglayout.debug.widget_update_flashing", WidgetUpdateFlashing, bool, false);
 
   DECL_GFX_PREF(Live, "ui.click_hold_context_menus.delay",     UiClickHoldContextMenusDelay, int32_t, 500);
 
   DECL_GFX_PREF(Once, "webgl.force-layers-readback",           WebGLForceLayersReadback, bool, false);
+  DECL_GFX_PREF(Once, "webgl.angle.try-d3d11",                 WebGLANGLETryD3D11, bool, false);
+  DECL_GFX_PREF(Once, "webgl.angle.force-d3d11",               WebGLANGLEForceD3D11, bool, false);
 
   DECL_GFX_PREF(Once, "layers.stereo-video.enabled",           StereoVideoEnabled, bool, false);
 public:
   // Manage the singleton:
   static gfxPrefs& GetSingleton()
   {
     MOZ_ASSERT(!sInstanceHasBeenDestroyed, "Should never recreate a gfxPrefs instance!");
     if (!sInstance) {

--- a/gfx/thebes/gfxWindowsPlatform.cpp
+++ b/gfx/thebes/gfxWindowsPlatform.cpp
@@ -472,16 +472,20 @@ gfxWindowsPlatform::CreateDevice(nsRefPt
   decltype(D3D10CreateDevice1)* createD3DDevice =
     (decltype(D3D10CreateDevice1)*) GetProcAddress(d3d10module, "D3D10CreateDevice1");
   if (!createD3DDevice)
     return E_FAIL;
 
   nsRefPtr<ID3D10Device1> device;
   HRESULT hr =
     createD3DDevice(adapter1, D3D10_DRIVER_TYPE_HARDWARE, nullptr,
+#ifdef DEBUG
+                    // This isn't set because of bug 1078411
+                    // D3D10_CREATE_DEVICE_DEBUG |
+#endif
                     D3D10_CREATE_DEVICE_BGRA_SUPPORT |
                     D3D10_CREATE_DEVICE_PREVENT_INTERNAL_THREADING_OPTIMIZATIONS,
                     static_cast<D3D10_FEATURE_LEVEL1>(kSupportedFeatureLevels[featureLevelIndex]),
                     D3D10_1_SDK_VERSION, getter_AddRefs(device));
 
   // If we fail here, the DirectX version or video card probably
   // changed.  We previously could use 10.1 but now we can't
   // anymore.  Revert back to doing a 10.0 check first before