Make IsSolidColor() a property on CC scrollbar layers.

webkit/renderer/compositor_bindings/web_scrollbar_layer_impl.cc

 // Copyright 2012 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 "webkit/renderer/compositor_bindings/web_scrollbar_layer_impl.h"
 
+#include "cc/base/switches.h"
 #include "cc/layers/scrollbar_layer.h"
 #include "third_party/WebKit/public/platform/WebScrollbar.h"
 #include "webkit/renderer/compositor_bindings/scrollbar_impl.h"
 #include "webkit/renderer/compositor_bindings/web_layer_impl.h"
 
 using cc::ScrollbarLayer;
 
 namespace webkit {
 
 WebScrollbarLayerImpl::WebScrollbarLayerImpl(
     WebKit::WebScrollbar* scrollbar,
     WebKit::WebScrollbarThemePainter painter,
     WebKit::WebScrollbarThemeGeometry* geometry)
-    : layer_(new WebLayerImpl(ScrollbarLayer::Create(
-          scoped_ptr<cc::Scrollbar>(new ScrollbarImpl(
-              make_scoped_ptr(scrollbar),
-              painter,
-              make_scoped_ptr(geometry))).Pass(), 0))) {}
+    : layer_(new WebLayerImpl(
+          ScrollbarLayer::Create(scoped_ptr<cc::Scrollbar>(new ScrollbarImpl(
+                                     make_scoped_ptr(scrollbar),
+                                     painter,
+                                     make_scoped_ptr(geometry))).Pass(),
+                                 0,
+                                 cc::switches::ForceSolidColorScrollbars()))) {}
 
 WebScrollbarLayerImpl::~WebScrollbarLayerImpl() {}
 
 WebKit::WebLayer* WebScrollbarLayerImpl::layer() { return layer_.get(); }
 
 void WebScrollbarLayerImpl::setScrollLayer(WebKit::WebLayer* layer) {
   int id = layer ? static_cast<WebLayerImpl*>(layer)->layer()->id() : 0;
   static_cast<ScrollbarLayer*>(layer_->layer())->SetScrollLayerId(id);
 }
 
 }  // namespace webkit