Clear renderer compositor trees if new page does not render in 4 seconds

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 <stddef.h>
 #include <stdint.h>
 
@@ skipping 431 matching lines @@
 
   void ElementIsAnimatingChanged(ElementId element_id,
                                  ElementListType list_type,
                                  const PropertyAnimationState& mask,
                                  const PropertyAnimationState& state) override;
 
   void ScrollOffsetAnimationFinished() override {}
   gfx::ScrollOffset GetScrollOffsetForAnimation(
       ElementId element_id) const override;
 
+  void ResetTrees();
+
  protected:
   LayerTreeHost(InitParams* params, CompositorMode mode);
 
   void InitializeThreaded(
       scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
       scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner);
   void InitializeSingleThreaded(
       LayerTreeHostSingleThreadClient* single_thread_client,
       scoped_refptr<base::SingleThreadTaskRunner> main_task_runner);
   void InitializeForTesting(
@@ skipping 136 matching lines @@
   MutatorHost* mutator_host_;
 
   scoped_refptr<base::SequencedTaskRunner> image_worker_task_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHost);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_H_