Allow WebExternalTextureLayers to receive a bitmap along with a mailbox

cc/trees/layer_tree_host.h

Index: cc/trees/layer_tree_host.h
diff --git a/cc/trees/layer_tree_host.h b/cc/trees/layer_tree_host.h
index b2856043c412a5a94428af2f851933b14d42b625..5744d0fe4f0dd4b67940acb8d5f85ba2f99b99b7 100644
--- a/cc/trees/layer_tree_host.h
+++ b/cc/trees/layer_tree_host.h
@@ -80,6 +80,7 @@ struct CC_EXPORT RendererCapabilities {
   int max_texture_size;
   bool avoid_pow2_textures;
   bool using_map_image;
+  bool using_shared_memory_resources;
 };
 
 class CC_EXPORT LayerTreeHost : NON_EXPORTED_BASE(public RateLimiterClient) {
@@ -255,6 +256,8 @@ class CC_EXPORT LayerTreeHost : NON_EXPORTED_BASE(public RateLimiterClient) {
 
   bool in_paint_layer_contents() const { return in_paint_layer_contents_; }
 
+  bool UsingSharedMemoryResources();
+
  protected:
   LayerTreeHost(LayerTreeHostClient* client, const LayerTreeSettings& settings);
   bool Initialize(scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner);