Route Scroll events through a cc::InputHandler

ui/compositor/layer.cc

 // Copyright (c) 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 "ui/compositor/layer.h"
 
 #include <algorithm>
 #include <memory>
 #include <utility>
 
@@ skipping 819 matching lines @@
     delegate_->OnDelegatedFrameDamage(damage_rect_in_dip);
 }
 
 void Layer::SetScrollable(Layer* parent_clip_layer,
                           const base::Closure& on_scroll) {
   cc_layer_->SetScrollClipLayerId(parent_clip_layer->cc_layer_->id());
   cc_layer_->set_did_scroll_callback(on_scroll);
   cc_layer_->SetUserScrollable(true, true);
 }
 
+cc::ElementId Layer::GetElementId() const {
+  return cc_layer_->element_id();
+}
+
 gfx::ScrollOffset Layer::CurrentScrollOffset() const {
   const Compositor* compositor = GetCompositor();
   gfx::ScrollOffset offset;
   if (compositor &&
       compositor->GetScrollOffsetForLayer(cc_layer_->id(), &offset))
     return offset;
   return cc_layer_->scroll_offset();
 }
 
 void Layer::SetScrollOffset(const gfx::ScrollOffset& offset) {
@@ skipping 325 matching lines @@
   const auto it = std::find_if(mirrors_.begin(), mirrors_.end(),
       [mirror](const std::unique_ptr<LayerMirror>& mirror_ptr) {
         return mirror_ptr.get() == mirror;
       });
 
   DCHECK(it != mirrors_.end());
   mirrors_.erase(it);
 }
 
 }  // namespace ui