cc: Make LTHI::LayerTreeSettings const

cc/trees/layer_tree_host_impl.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_IMPL_H_
 #define CC_TREES_LAYER_TREE_HOST_IMPL_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 658 matching lines @@
   ScopedPtrVector<SwapPromise> swap_promises_for_main_thread_scroll_update_;
 
   // An object to implement the ScrollElasticityHelper interface and
   // hold all state related to elasticity. May be NULL if never requested.
   scoped_ptr<ScrollElasticityHelper> scroll_elasticity_helper_;
 
   bool tile_priorities_dirty_;
 
   // The optional delegate for the root layer scroll offset.
   LayerScrollOffsetDelegate* root_layer_scroll_offset_delegate_;
-  LayerTreeSettings settings_;
+  const LayerTreeSettings settings_;
   LayerTreeDebugState debug_state_;
   bool visible_;
   ManagedMemoryPolicy cached_managed_memory_policy_;
 
   gfx::Vector2dF accumulated_root_overscroll_;
 
   bool pinch_gesture_active_;
   bool pinch_gesture_end_should_clear_scrolling_layer_;
   gfx::Point previous_pinch_anchor_;
 
@@ skipping 67 matching lines @@
   scoped_ptr<FrameTimingTracker> frame_timing_tracker_;
 
   scoped_ptr<Viewport> viewport_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_IMPL_H_