Fix solid color scrollbars for sublayers.

cc/layers/layer_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/layers/layer_impl.h"
 
 #include "base/debug/trace_event.h"
 #include "base/stringprintf.h"
 #include "base/values.h"
 #include "cc/animation/animation_registrar.h"
@@ skipping 782 matching lines @@
   // Base LayerImpl has all of its content scales and content bounds pushed
   // from its Layer during commit and just reuses those values as-is.
   *contents_scale_x = this->contents_scale_x();
   *contents_scale_y = this->contents_scale_y();
   *content_bounds = this->content_bounds();
 }
 
 void LayerImpl::UpdateScrollbarPositions() {
   gfx::Vector2dF current_offset = scroll_offset_ + scroll_delta_;
 
+  gfx::RectF viewport(PointAtOffsetFromOrigin(current_offset), bounds_);
+  gfx::SizeF scrollable_size(max_scroll_offset_.x() + bounds_.width(),
+                             max_scroll_offset_.y() + bounds_.height());
   if (horizontal_scrollbar_layer_) {
     horizontal_scrollbar_layer_->SetCurrentPos(current_offset.x());
     horizontal_scrollbar_layer_->SetTotalSize(bounds_.width());
     horizontal_scrollbar_layer_->SetMaximum(max_scroll_offset_.x());
+    horizontal_scrollbar_layer_->SetViewportWithinScrollableArea(
+        viewport, scrollable_size);
   }
   if (vertical_scrollbar_layer_) {
     vertical_scrollbar_layer_->SetCurrentPos(current_offset.y());
     vertical_scrollbar_layer_->SetTotalSize(bounds_.height());
     vertical_scrollbar_layer_->SetMaximum(max_scroll_offset_.y());
+    vertical_scrollbar_layer_->SetViewportWithinScrollableArea(
+        viewport, scrollable_size);
   }
 
   if (current_offset == last_scroll_offset_)
     return;
   last_scroll_offset_ = current_offset;
 
   if (scrollbar_animation_controller_ &&
       !scrollbar_animation_controller_->IsScrollGestureInProgress()) {
     scrollbar_animation_controller_->DidProgrammaticallyUpdateScroll(
         base::TimeTicks::Now());
@@ skipping 135 matching lines @@
 
 }
 
 scoped_ptr<base::Value> LayerImpl::AsValue() const {
   scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue());
   AsValueInto(state.get());
   return state.PassAs<base::Value>();
 }
 
 }  // namespace cc