Enable partial texture upload support for browser compositor with Surfaces

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_host_impl.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/basictypes.h"
@@ skipping 273 matching lines @@
   // values were applied and committed.
   if (CommitEarlyOutHandledCommit(reason)) {
     active_tree_->ApplySentScrollAndScaleDeltasFromAbortedCommit();
     active_tree_->ResetContentsTexturesPurged();
   }
 }
 
 void LayerTreeHostImpl::BeginCommit() {
   TRACE_EVENT0("cc", "LayerTreeHostImpl::BeginCommit");
 
+  // Ensure all textures are returned so partial texture updates can happen
+  // during the commit. Impl-side-painting doesn't upload during commits, so
+  // is unaffected.
+  if (!settings_.impl_side_painting)
+    output_surface_->ForceReclaimResources();
+
   if (UsePendingTreeForSync())
     CreatePendingTree();
 }
 
 void LayerTreeHostImpl::CommitComplete() {
   TRACE_EVENT0("cc", "LayerTreeHostImpl::CommitComplete");
 
   if (pending_tree_)
     pending_tree_->ApplyScrollDeltasSinceBeginMainFrame();
   sync_tree()->set_needs_update_draw_properties();
@@ skipping 3173 matching lines @@
 }
 
 void LayerTreeHostImpl::UnregisterPictureLayerImpl(PictureLayerImpl* layer) {
   std::vector<PictureLayerImpl*>::iterator it =
       std::find(picture_layers_.begin(), picture_layers_.end(), layer);
   DCHECK(it != picture_layers_.end());
   picture_layers_.erase(it);
 }
 
 }  // namespace cc