Make scrollable viewport size no longer depend on clip layer.

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 "base/basictypes.h"
 #include "base/json/json_writer.h"
@@ skipping 1273 matching lines @@
 }
 
 float LayerTreeHostImpl::DeviceScaleFactor() const {
   return device_scale_factor_;
 }
 
 gfx::SizeF LayerTreeHostImpl::VisibleViewportSize() const {
   gfx::SizeF dip_size =
       gfx::ScaleSize(device_viewport_size(), 1.f / device_scale_factor());
 
-  // The clip layer should be used if non-overlay scrollbars may exist since
-  // it adjusts for them.
-  LayerImpl* clip_layer = active_tree_->RootClipLayer();
-  if (!Settings().solid_color_scrollbars && clip_layer &&
-      clip_layer->masks_to_bounds())
-    dip_size = clip_layer->bounds();
-
   float top_offset =
       top_controls_manager_ ? top_controls_manager_->content_top_offset() : 0.f;
   return gfx::SizeF(dip_size.width(),
                     dip_size.height() - top_offset - overdraw_bottom_height_);
 }
 
 const LayerTreeSettings& LayerTreeHostImpl::Settings() const {
   return settings();
 }
 
@@ skipping 1062 matching lines @@
   if (LayerTreeDebugState::Equal(debug_state_, new_debug_state))
     return;
   if (debug_state_.continuous_painting != new_debug_state.continuous_painting)
     paint_time_counter_->ClearHistory();
 
   debug_state_ = new_debug_state;
   SetFullRootLayerDamage();
 }
 
 }  // namespace cc