Hide pinch viewport scrollbars when near minimum scale.

cc/layers/scrollbar_layer_impl_base.cc

 // Copyright 2013 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/layers/scrollbar_layer_impl_base.h"
 
 #include <algorithm>
 #include "cc/trees/layer_tree_impl.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 
@@ skipping 15 matching lines @@
       orientation_(orientation),
       is_left_side_vertical_scrollbar_(is_left_side_vertical_scrollbar),
       vertical_adjust_(0.f),
       visible_to_total_length_ratio_(1.f) {
 }
 
 ScrollbarLayerImplBase::~ScrollbarLayerImplBase() {}
 
 void ScrollbarLayerImplBase::PushPropertiesTo(LayerImpl* layer) {
   float active_opacity = layer->opacity();
+  bool active_hidden = layer->hide_layer_and_subtree();
   LayerImpl::PushPropertiesTo(layer);
   layer->SetOpacity(active_opacity);
+  layer->SetHideLayerAndSubtree(active_hidden);
   DCHECK(layer->ToScrollbarLayer());
   layer->ToScrollbarLayer()->set_is_overlay_scrollbar(is_overlay_scrollbar_);
   PushScrollClipPropertiesTo(layer);
 }
 
 void ScrollbarLayerImplBase::PushScrollClipPropertiesTo(LayerImpl* layer) {
   DCHECK(layer->ToScrollbarLayer());
   layer->ToScrollbarLayer()->SetScrollLayerAndClipLayerByIds(ScrollLayerId(),
                                                              ClipLayerId());
 }
@@ skipping 203 matching lines @@
 }
 
 void ScrollbarLayerImplBase::ScrollbarParametersDidChange(bool on_resize) {
   if (!clip_layer_ || !scroll_layer_)
     return;
 
   scroll_layer_->SetScrollbarPosition(this, clip_layer_, on_resize);
 }
 
 }  // namespace cc