Bug 1194472 - Correctly fetch compositor backend in WebGLContext. r=jgilbert

--HG--
extra : rebase_source : 9e0b5ba81b819b5b179e56dc7c4e1454a660b448

dom/canvas/WebGLContext.cpp

@@ -672,6 +672,7 @@ PopulateCapFallbackQueue(const SurfaceCaps& baseCaps,
 static bool
 CreateOffscreen(GLContext* gl, const WebGLContextOptions& options,
                 const nsCOMPtr<nsIGfxInfo>& gfxInfo, WebGLContext* webgl,
+                layers::LayersBackend layersBackend,
                 layers::ISurfaceAllocator* surfAllocator)
 {
     SurfaceCaps baseCaps;
@@ -689,7 +690,7 @@ CreateOffscreen(GLContext* gl, const WebGLContextOptions& options,
 
     if (gl->IsANGLE() ||
         (gl->GetContextType() == GLContextType::GLX &&
-         gfxPlatform::GetPlatform()->GetCompositorBackend() == LayersBackend::LAYERS_OPENGL))
+         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
@@ -763,7 +764,8 @@ WebGLContext::CreateOffscreenGL(bool forceEnabled)
         if (!gl)
             break;
 
-        if (!CreateOffscreen(gl, mOptions, gfxInfo, this, surfAllocator))
+        if (!CreateOffscreen(gl, mOptions, gfxInfo, this,
+                             GetCompositorBackendType(), surfAllocator))
             break;
 
         if (!InitAndValidateGL())
@@ -1292,6 +1294,17 @@ WebGLContext::GetCanvasLayer(nsDisplayListBuilder* builder,
     return canvasLayer.forget();
 }
 
+layers::LayersBackend
+WebGLContext::GetCompositorBackendType() const
+{
+    nsIWidget* docWidget = nsContentUtils::WidgetForDocument(mCanvasElement->OwnerDoc());
+    if (docWidget) {
+        layers::LayerManager* layerManager = docWidget->GetLayerManager();
+        return layerManager->GetCompositorBackendType();
+    }
+    return LayersBackend::LAYERS_NONE;
+}
+
 void
 WebGLContext::GetContextAttributes(dom::Nullable<dom::WebGLContextAttributes>& retval)
 {

dom/canvas/WebGLContext.h

@@ -363,6 +363,8 @@ public:
         return IsContextLost() ? 0 : mHeight;
     }
 
+    layers::LayersBackend GetCompositorBackendType() const;
+
     void
     GetContextAttributes(dom::Nullable<dom::WebGLContextAttributes>& retval);