Implement pinch-zoom scaling for main-frame scrollbars and pinch-zoom overlay scrollbars.

cc/layer.cc

 // Copyright 2010 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/layer.h"
 
 #include "cc/animation.h"
 #include "cc/animation_events.h"
 #include "cc/layer_animation_controller.h"
 #include "cc/layer_impl.h"
 #include "cc/layer_tree_host.h"
 #include "cc/layer_tree_impl.h"
 #include "third_party/WebKit/Source/Platform/chromium/public/WebAnimationDelegate.h"
 #include "third_party/WebKit/Source/Platform/chromium/public/WebLayerScrollClient.h"
 #include "third_party/WebKit/Source/Platform/chromium/public/WebSize.h"
 #include "third_party/skia/include/core/SkImageFilter.h"
 #include "ui/gfx/rect_conversions.h"
 
 namespace cc {
 
+const int Layer::s_invalidLayerId = -1;
 static int s_nextLayerId = 1;
 
 scoped_refptr<Layer> Layer::create()
 {
     return make_scoped_refptr(new Layer());
 }
 
 Layer::Layer()
     : m_needsDisplay(false)
     , m_stackingOrderChanged(false)
@@ skipping 873 matching lines @@
 {
     return 0;
 }
 
 void sortLayers(std::vector<scoped_refptr<Layer> >::iterator, std::vector<scoped_refptr<Layer> >::iterator, void*)
 {
     // Currently we don't use z-order to decide what to paint, so there's no need to actually sort Layers.
 }
 
 }  // namespace cc