Bug 1188752: Ensure persistence of DrawTarget when using InitializeWithSurface. r=jrmuizel

dom/canvas/CanvasRenderingContext2D.cpp

@@ -5446,12 +5446,7 @@ CanvasRenderingContext2D::GetBufferProvider(LayerManager* aManager)
     return nullptr;
   }
 
-  mBufferProvider = aManager->CreatePersistentBufferProvider(mTarget->GetSize(), mTarget->GetFormat());
-
-  RefPtr<SourceSurface> surf = mTarget->Snapshot();
-
-  mTarget = mBufferProvider->GetDT(IntRect(IntPoint(), mTarget->GetSize()));
-  mTarget->CopySurface(surf, IntRect(IntPoint(), mTarget->GetSize()), IntPoint());
+  mBufferProvider = new PersistentBufferProviderBasic(mTarget);
 
   return mBufferProvider;
 }

gfx/layers/PersistentBufferProvider.h

@@ -59,6 +59,7 @@ public:
 
   PersistentBufferProviderBasic(LayerManager* aManager, gfx::IntSize aSize,
                                 gfx::SurfaceFormat aFormat, gfx::BackendType aBackend);
+  PersistentBufferProviderBasic(gfx::DrawTarget* aTarget) : mDrawTarget(aTarget) {}
 
   bool IsValid() { return !!mDrawTarget; }
   virtual LayersBackend GetType() { return LayersBackend::LAYERS_BASIC; }