Bug 897409. Use a temporary surface instead of forcing image surfaces. r=mattwoodrow

gfx/layers/CopyableCanvasLayer.cpp

@@ -74,11 +74,6 @@ CopyableCanvasLayer::UpdateSurface(gfxASurface* aDestSurface, Layer* aMaskLayer)
   }
 
   if (mGLContext) {
-    if (aDestSurface && aDestSurface->GetType() != gfxASurface::SurfaceTypeImage) {
-      MOZ_ASSERT(false, "Destination surface must be ImageSurface type.");
-      return;
-    }
-
     nsRefPtr<gfxImageSurface> readSurf;
     nsRefPtr<gfxImageSurface> resultSurf;
 
@@ -93,9 +88,9 @@ CopyableCanvasLayer::UpdateSurface(gfxASurface* aDestSurface, Layer* aMaskLayer)
                             ? gfxASurface::ImageFormatRGB24
                             : gfxASurface::ImageFormatARGB32;
 
-    if (aDestSurface) {
-      resultSurf = static_cast<gfxImageSurface*>(aDestSurface);
-    } else {
+    bool needsTempSurface = !aDestSurface ||
+                            !(resultSurf = aDestSurface->GetAsImageSurface());
+    if (needsTempSurface) {
       resultSurf = GetTempSurface(readSize, format);
     }
     MOZ_ASSERT(resultSurf);
@@ -156,7 +151,7 @@ CopyableCanvasLayer::UpdateSurface(gfxASurface* aDestSurface, Layer* aMaskLayer)
     }
 
     // stick our surface into mSurface, so that the Paint() path is the same
-    if (!aDestSurface) {
+    if (needsTempSurface) {
       mSurface = resultSurf;
     }
   }

gfx/layers/client/CanvasClient.cpp

@@ -66,7 +66,7 @@ CanvasClient2D::Update(gfx::IntSize aSize, ClientCanvasLayer* aLayer)
                                               : gfxASurface::CONTENT_COLOR_ALPHA;
   mDeprecatedTextureClient->EnsureAllocated(aSize, contentType);
 
-  gfxASurface* surface = mDeprecatedTextureClient->LockImageSurface();
+  gfxASurface* surface = mDeprecatedTextureClient->LockSurface();
   aLayer->UpdateSurface(surface);
   mDeprecatedTextureClient->Unlock();
 }