Fix smooth scroll jump when switching scroll handling between MT and CC

cc/layers/layer_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_LAYERS_LAYER_IMPL_H_
 #define CC_LAYERS_LAYER_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 490 matching lines @@
   bool user_scrollable_vertical() const { return user_scrollable_vertical_; }
 
   bool user_scrollable(ScrollbarOrientation orientation) const;
 
   void ApplySentScrollDeltasFromAbortedCommit();
 
   void set_main_thread_scrolling_reasons(
       uint32_t main_thread_scrolling_reasons) {
     main_thread_scrolling_reasons_ = main_thread_scrolling_reasons;
   }
-
   uint32_t main_thread_scrolling_reasons() const {
     return main_thread_scrolling_reasons_;
   }
-
   bool should_scroll_on_main_thread() const {
     return !!main_thread_scrolling_reasons_;
   }
 
   void SetNonFastScrollableRegion(const Region& region) {
     non_fast_scrollable_region_ = region;
   }
   const Region& non_fast_scrollable_region() const {
     return non_fast_scrollable_region_;
   }
@@ skipping 350 matching lines @@
   // If true, the layer or one of its descendants has a touch handler.
   bool layer_or_descendant_has_touch_handler_;
   bool sorted_for_recursion_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_