Make IsSolidColor() a property on CC scrollbar layers.

cc/test/fake_scrollbar_layer.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 "cc/test/fake_scrollbar_layer.h"
 
 #include "cc/resources/resource_update_queue.h"
 #include "cc/test/fake_scrollbar.h"
 
 namespace cc {
 
 FakeScrollbarLayer::FakeScrollbarLayer(bool paint_during_update,
                                        bool has_thumb,
-                                       int scrolling_layer_id)
+                                       int scrolling_layer_id,
+                                       bool is_solid_color)
     : ScrollbarLayer(
           scoped_ptr<Scrollbar>(
               new FakeScrollbar(paint_during_update, has_thumb, false)).Pass(),
-          scrolling_layer_id),
+          scrolling_layer_id,
+          is_solid_color),
       update_count_(0),
       last_update_full_upload_size_(0),
       last_update_partial_upload_size_(0) {
   SetAnchorPoint(gfx::PointF(0.f, 0.f));
   SetBounds(gfx::Size(1, 1));
   SetIsDrawable(true);
 }
 
 FakeScrollbarLayer::~FakeScrollbarLayer() {}
 
 void FakeScrollbarLayer::Update(ResourceUpdateQueue* queue,
                                 const OcclusionTracker* occlusion) {
   size_t full = queue->FullUploadSize();
   size_t partial = queue->PartialUploadSize();
   ScrollbarLayer::Update(queue, occlusion);
   update_count_++;
   last_update_full_upload_size_ = queue->FullUploadSize() - full;
   last_update_partial_upload_size_ = queue->PartialUploadSize() - partial;
 }
 
 }  // namespace cc