cc: Add CopyResource function to ResourceProvider API.

cc/resources/resource_provider.h

Index: cc/resources/resource_provider.h
diff --git a/cc/resources/resource_provider.h b/cc/resources/resource_provider.h
index ad5589c1c8b2605d1025e3c2ee8f2e7e681afede..62930bb29a58effa02413e9ddc4bedfa30470039 100644
--- a/cc/resources/resource_provider.h
+++ b/cc/resources/resource_provider.h
@@ -370,6 +370,9 @@ class CC_EXPORT ResourceProvider {
   // Indicates if we can currently lock this resource for write.
   bool CanLockForWrite(ResourceId id);
 
+  // Copy pixels from source to destination.
+  void CopyResource(ResourceId source_id, ResourceId dest_id);
+
   static GLint GetActiveTextureUnit(gpu::gles2::GLES2Interface* gl);
 
  private:
@@ -409,6 +412,8 @@ class CC_EXPORT ResourceProvider {
     unsigned gl_pixel_buffer_id;
     // Query used to determine when asynchronous set pixels complete.
     unsigned gl_upload_query_id;
+    // Query used to determine when read lock fence has passed.
+    unsigned gl_read_lock_query_id;
     TextureMailbox mailbox;
     ReleaseCallback release_callback;
     uint8_t* pixels;