Remove GraphicsLayer::didScroll and directly call ScrollableArea::didScroll

cc/layers/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/layers/layer.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 805 matching lines @@
     transform_node->scroll_offset = CurrentScrollOffset();
     transform_node->needs_local_transform_update = true;
     property_trees->transform_tree.set_needs_update(true);
     needs_rebuild = false;
   }
 
   if (needs_rebuild)
     property_trees->needs_rebuild = true;
 
   if (!inputs_.did_scroll_callback.is_null())
-    inputs_.did_scroll_callback.Run();
+    inputs_.did_scroll_callback.Run(scroll_offset);
+
   // The callback could potentially change the layer structure:
   // "this" may have been destroyed during the process.
 }
 
 void Layer::SetScrollClipLayerId(int clip_layer_id) {
   DCHECK(IsPropertyChangeAllowed());
   if (inputs_.scroll_clip_layer_id == clip_layer_id)
     return;
   inputs_.scroll_clip_layer_id = clip_layer_id;
   SetNeedsCommit();
@@ skipping 736 matching lines @@
       ->num_copy_requests_in_subtree;
 }
 
 gfx::Transform Layer::screen_space_transform() const {
   DCHECK_NE(transform_tree_index_, TransformTree::kInvalidNodeId);
   return draw_property_utils::ScreenSpaceTransform(
       this, layer_tree_host_->property_trees()->transform_tree);
 }
 
 }  // namespace cc