Re-land: cc: Implement shared worker contexts.

cc/trees/layer_tree_host.h

 // 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.
 
 #ifndef CC_TREES_LAYER_TREE_HOST_H_
 #define CC_TREES_LAYER_TREE_HOST_H_
 
 #include <limits>
 #include <set>
 #include <string>
@@ skipping 416 matching lines @@
   bool needs_full_tree_sync_;
   bool needs_meta_info_recomputation_;
 
   LayerTreeHostClient* client_;
   scoped_ptr<Proxy> proxy_;
 
   int source_frame_number_;
   int meta_information_sequence_number_;
   scoped_ptr<RenderingStatsInstrumentation> rendering_stats_instrumentation_;
 
+  // |current_output_surface_| can't be updated until we've successfully
+  // initialized a new output surface. |new_output_surface_| contains the
+  // new output surface that is currently being initialized. If initialization
+  // is successful then |new_output_surface_| replaces
+  // |current_output_surface_|.
+  scoped_ptr<OutputSurface> new_output_surface_;
+  scoped_ptr<OutputSurface> current_output_surface_;
   bool output_surface_lost_;
 
   scoped_refptr<Layer> root_layer_;
   scoped_refptr<HeadsUpDisplayLayer> hud_layer_;
 
   base::WeakPtr<InputHandler> input_handler_weak_ptr_;
   base::WeakPtr<TopControlsManager> top_controls_manager_weak_ptr_;
 
   const LayerTreeSettings settings_;
   LayerTreeDebugState debug_state_;
@@ skipping 55 matching lines @@
 
   uint32_t surface_id_namespace_;
   uint32_t next_surface_sequence_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHost);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_H_