cc: Add CopyResource function to ResourceProvider API.

cc/resources/pixel_buffer_raster_worker_pool.cc

Index: cc/resources/pixel_buffer_raster_worker_pool.cc
diff --git a/cc/resources/pixel_buffer_raster_worker_pool.cc b/cc/resources/pixel_buffer_raster_worker_pool.cc
index 4383acc751c63aebeba3b2a2bb4c6a9a41831994..4c8ca7b6221a76067599b8e57d85e5f8fb7819cb 100644
--- a/cc/resources/pixel_buffer_raster_worker_pool.cc
+++ b/cc/resources/pixel_buffer_raster_worker_pool.cc
@@ -401,6 +401,11 @@ void PixelBufferRasterWorkerPool::CheckForCompletedUploads() {
     task->CompleteOnOriginThread(this);
     task->DidComplete();
 
+    // Async set pixels commands are not necessarily processed in-sequence with
+    // drawing commands. Read lock fences are required to ensure that async
+    // commands don't access the resource while used for drawing.
+    resource_provider_->EnableReadLockFences(task->resource()->id(), true);
+
     DCHECK(std::find(completed_raster_tasks_.begin(),
                      completed_raster_tasks_.end(),
                      task) == completed_raster_tasks_.end());