Allow WebExternalTextureLayers to receive a bitmap along with a mailbox

cc/layers/texture_layer.h

Index: cc/layers/texture_layer.h
diff --git a/cc/layers/texture_layer.h b/cc/layers/texture_layer.h
index e050533d22457908c24fcd37f53022f81136fd1d..d2037ce18654a0122b6cf2ad79fdc9263ec6b0e8 100644
--- a/cc/layers/texture_layer.h
+++ b/cc/layers/texture_layer.h
@@ -67,6 +67,10 @@ class CC_EXPORT TextureLayer : public Layer {
 
   void WillModifyTexture();
 
+  // Returns true if the layer must use a mailbox with shared memory or an
+  // SkBitmap.
+  bool MustUseBitmap();
+
   virtual void SetNeedsDisplayRect(const gfx::RectF& dirty_rect) OVERRIDE;
 
   virtual void SetLayerTreeHost(LayerTreeHost* layer_tree_host) OVERRIDE;