Make scroll offset type of float in cc

cc/trees/layer_tree_host_common.h

 // Copyright 2011 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.
 
 #ifndef CC_TREES_LAYER_TREE_HOST_COMMON_H_
 #define CC_TREES_LAYER_TREE_HOST_COMMON_H_
 
 #include <limits>
 #include <vector>
 
@@ skipping 112 matching lines @@
     return layers[index];
   }
 
   static LayerImpl* get_layer_as_raw_ptr(const LayerImplList& layers,
                                          size_t index) {
     return layers[index];
   }
 
   struct ScrollUpdateInfo {
     int layer_id;
+    // TODO(miletus) : Use ScrollOffset once LayerTreeHost/Blink fully supports
+    // franctional scroll offset.
     gfx::Vector2d scroll_delta;
   };
 };
 
 struct CC_EXPORT ScrollAndScaleSet {
   ScrollAndScaleSet();
   ~ScrollAndScaleSet();
 
   std::vector<LayerTreeHostCommon::ScrollUpdateInfo> scrolls;
   float page_scale_delta;
@@ skipping 105 matching lines @@
           false,
           render_surface_layer_list,
           0) {
   DCHECK(root_layer);
   DCHECK(render_surface_layer_list);
 }
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_COMMON_H_