--- a/dom/canvas/WebGL2ContextState.cpp
+++ b/dom/canvas/WebGL2ContextState.cpp
@@ -7,57 +7,136 @@
 #include "WebGL2Context.h"
 #include "WebGLContextUtils.h"
 
 namespace mozilla {
 
 JS::Value
 WebGL2Context::GetParameter(JSContext* cx, GLenum pname, ErrorResult& rv)
 {
+  // The following cases are handled in WebGLContext::GetParameter():
+  //     case LOCAL_GL_MAX_COLOR_ATTACHMENTS:
+  //     case LOCAL_GL_MAX_DRAW_BUFFERS:
+  //     case LOCAL_GL_DRAW_BUFFERi:
+
   if (IsContextLost())
     return JS::NullValue();
 
   MakeContextCurrent();
 
   switch (pname) {
+    /* GLboolean */
+    case LOCAL_GL_RASTERIZER_DISCARD:
+    case LOCAL_GL_SAMPLE_ALPHA_TO_COVERAGE:
+    case LOCAL_GL_SAMPLE_COVERAGE:
+    case LOCAL_GL_TRANSFORM_FEEDBACK_PAUSED:
+    case LOCAL_GL_TRANSFORM_FEEDBACK_ACTIVE:
+    case LOCAL_GL_UNPACK_SKIP_IMAGES:
+    case LOCAL_GL_UNPACK_SKIP_PIXELS:
+    case LOCAL_GL_UNPACK_SKIP_ROWS: {
+      realGLboolean b = 0;
+      gl->fGetBooleanv(pname, &b);
+      return JS::BooleanValue(bool(b));
+    }
+
+    /* GLenum */
+    case LOCAL_GL_FRAGMENT_SHADER_DERIVATIVE_HINT:
+    case LOCAL_GL_READ_BUFFER:
+      /* fall through */
+
+    /* GLint */
+    case LOCAL_GL_MAX_3D_TEXTURE_SIZE:
+    case LOCAL_GL_MAX_ARRAY_TEXTURE_LAYERS:
+    case LOCAL_GL_MAX_COMBINED_UNIFORM_BLOCKS:
+    case LOCAL_GL_MAX_ELEMENTS_INDICES:
+    case LOCAL_GL_MAX_ELEMENTS_VERTICES:
+    case LOCAL_GL_MAX_FRAGMENT_INPUT_COMPONENTS:
+    case LOCAL_GL_MAX_FRAGMENT_UNIFORM_BLOCKS:
+    case LOCAL_GL_MAX_FRAGMENT_UNIFORM_COMPONENTS:
+    case LOCAL_GL_MAX_PROGRAM_TEXEL_OFFSET:
     case LOCAL_GL_MAX_SAMPLES:
-    case LOCAL_GL_MAX_UNIFORM_BLOCK_SIZE:
-    case LOCAL_GL_MAX_VERTEX_UNIFORM_COMPONENTS: {
+    case LOCAL_GL_MAX_TEXTURE_LOD_BIAS:
+    case LOCAL_GL_MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS:
+    case LOCAL_GL_MAX_TRANSFORM_FEEDBACK_SEPARATE_ATTRIBS:
+    case LOCAL_GL_MAX_TRANSFORM_FEEDBACK_SEPARATE_COMPONENTS:
+    case LOCAL_GL_MAX_UNIFORM_BUFFER_BINDINGS:
+    case LOCAL_GL_MAX_VARYING_COMPONENTS:
+    case LOCAL_GL_MAX_VERTEX_OUTPUT_COMPONENTS:
+    case LOCAL_GL_MAX_VERTEX_UNIFORM_BLOCKS:
+    case LOCAL_GL_MAX_VERTEX_UNIFORM_COMPONENTS:
+    case LOCAL_GL_MIN_PROGRAM_TEXEL_OFFSET:
+    case LOCAL_GL_PACK_ROW_LENGTH:
+    case LOCAL_GL_PACK_SKIP_PIXELS:
+    case LOCAL_GL_PACK_SKIP_ROWS:
+    case LOCAL_GL_UNIFORM_BUFFER_OFFSET_ALIGNMENT:
+    case LOCAL_GL_UNPACK_IMAGE_HEIGHT:
+    case LOCAL_GL_UNPACK_ROW_LENGTH: {
       GLint val;
       gl->fGetIntegerv(pname, &val);
-      return JS::NumberValue(uint32_t(val));
+      return JS::Int32Value(val);
     }
 
-    case LOCAL_GL_TEXTURE_BINDING_3D:
-      return WebGLObjectAsJSValue(cx, mBound3DTextures[mActiveTexture].get(), rv);
+    /* GLint64 */
+    //case LOCAL_GL_MAX_CLIENT_WAIT_TIMEOUT_WEBGL:
+    case LOCAL_GL_MAX_ELEMENT_INDEX:
+    case LOCAL_GL_MAX_COMBINED_FRAGMENT_UNIFORM_COMPONENTS:
+    case LOCAL_GL_MAX_COMBINED_VERTEX_UNIFORM_COMPONENTS:
+    case LOCAL_GL_MAX_SERVER_WAIT_TIMEOUT:
+    case LOCAL_GL_MAX_UNIFORM_BLOCK_SIZE: {
+      GLint64 val;
+      gl->fGetInteger64v(pname, &val);
+      return JS::DoubleValue(static_cast<double>(val));
+    }
 
-      // DRAW_FRAMEBUFFER_BINDING is the same as FRAMEBUFFER_BINDING.
-    case LOCAL_GL_READ_FRAMEBUFFER_BINDING:
-      return WebGLObjectAsJSValue(cx, mBoundReadFramebuffer.get(), rv);
+    case LOCAL_GL_COPY_READ_BUFFER_BINDING:
+      return WebGLObjectAsJSValue(cx, mBoundCopyReadBuffer.get(), rv);
+
+    case LOCAL_GL_COPY_WRITE_BUFFER_BINDING:
+      return WebGLObjectAsJSValue(cx, mBoundCopyWriteBuffer.get(), rv);
 
     case LOCAL_GL_PIXEL_PACK_BUFFER_BINDING:
       return WebGLObjectAsJSValue(cx, mBoundPixelPackBuffer.get(), rv);
 
     case LOCAL_GL_PIXEL_UNPACK_BUFFER_BINDING:
       return WebGLObjectAsJSValue(cx, mBoundPixelUnpackBuffer.get(), rv);
 
-    case LOCAL_GL_UNIFORM_BUFFER_BINDING:
-      return WebGLObjectAsJSValue(cx, mBoundUniformBuffer.get(), rv);
-
     case LOCAL_GL_TRANSFORM_FEEDBACK_BUFFER_BINDING:
       return WebGLObjectAsJSValue(cx, mBoundTransformFeedbackBuffer.get(), rv);
 
-    case LOCAL_GL_COPY_READ_BUFFER_BINDING:
-      return WebGLObjectAsJSValue(cx, mBoundCopyReadBuffer.get(), rv);
+    case LOCAL_GL_UNIFORM_BUFFER_BINDING:
+      return WebGLObjectAsJSValue(cx, mBoundUniformBuffer.get(), rv);
+
+    // DRAW_FRAMEBUFFER_BINDING is the same as FRAMEBUFFER_BINDING.
+    case LOCAL_GL_READ_FRAMEBUFFER_BINDING:
+      return WebGLObjectAsJSValue(cx, mBoundReadFramebuffer.get(), rv);
+
+    case LOCAL_GL_SAMPLER_BINDING:
+      // TODO: Implement bound sampler tracking
+      //return WebGLObjectAsJSValue(cx, mBoundSamplers[mActiveTexture].get(), rv);
+      return JS::NullValue();
 
-    case LOCAL_GL_COPY_WRITE_BUFFER_BINDING:
-      return WebGLObjectAsJSValue(cx, mBoundCopyWriteBuffer.get(), rv);
+    case LOCAL_GL_TEXTURE_BINDING_2D_ARRAY:
+      // TODO: Implement gl.TEXTURE_2D_ARRAY
+      // return WebGLObjectAsJSValue(cx, mBound2DTextureArrays[mActiveTexture].get(), rv);
+      return JS::NullValue();
+
+    case LOCAL_GL_TEXTURE_BINDING_3D:
+      return WebGLObjectAsJSValue(cx, mBound3DTextures[mActiveTexture].get(), rv);
 
-    case LOCAL_GL_MAX_TRANSFORM_FEEDBACK_SEPARATE_ATTRIBS:
-      return JS::Int32Value(mGLMaxTransformFeedbackSeparateAttribs);
+    case LOCAL_GL_TRANSFORM_FEEDBACK_BINDING: {
+      WebGLTransformFeedback* tf =
+        (mBoundTransformFeedback != mDefaultTransformFeedback) ? mBoundTransformFeedback.get() : nullptr;
+      return WebGLObjectAsJSValue(cx, tf, rv);
+    }
+
+    case LOCAL_GL_VERTEX_ARRAY_BINDING: {
+      WebGLVertexArray* vao =
+        (mBoundVertexArray != mDefaultVertexArray) ? mBoundVertexArray.get() : nullptr;
+      return WebGLObjectAsJSValue(cx, vao, rv);
+    }
 
     case LOCAL_GL_VERSION:
       return StringValue(cx, "WebGL 2.0", rv);
 
     case LOCAL_GL_SHADING_LANGUAGE_VERSION:
       return StringValue(cx, "WebGL GLSL ES 3.00", rv);
 
     default: