Add hints for potential overlay promotion on android.

cc/ipc/transferable_resource_struct_traits.h

Index: cc/ipc/transferable_resource_struct_traits.h
diff --git a/cc/ipc/transferable_resource_struct_traits.h b/cc/ipc/transferable_resource_struct_traits.h
index 52aa93dac103611e9b619429963b7a514ffd1611..f7f4ab0f4dfd4f379fd814fca5199921b8252b27 100644
--- a/cc/ipc/transferable_resource_struct_traits.h
+++ b/cc/ipc/transferable_resource_struct_traits.h
@@ -48,6 +48,16 @@ struct StructTraits<cc::mojom::TransferableResourceDataView,
     return resource.is_overlay_candidate;
   }
 
+  static bool is_backed_by_surface_texture(
+      const cc::TransferableResource& resource) {
+#if defined(OS_ANDROID)
+    // TransferableResource has this in an #ifdef, but mojo doesn't leta us.
+    return resource.is_backed_by_surface_texture;
+#else
+    return false;
+#endif
+  }
+
   static bool Read(cc::mojom::TransferableResourceDataView data,
                    cc::TransferableResource* out);
 };