Move viewport scrolling logic into separate class

cc/cc.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
@@ skipping 230 matching lines @@
         'layers/ui_resource_layer.h',
         'layers/ui_resource_layer_impl.cc',
         'layers/ui_resource_layer_impl.h',
         'layers/video_frame_provider.h',
         'layers/video_frame_provider_client_impl.cc',
         'layers/video_frame_provider_client_impl.h',
         'layers/video_layer.cc',
         'layers/video_layer.h',
         'layers/video_layer_impl.cc',
         'layers/video_layer_impl.h',
+        'layers/viewport.cc',
+        'layers/viewport.h',
         'output/begin_frame_args.cc',
         'output/begin_frame_args.h',
         'output/bsp_tree.cc',
         'output/bsp_tree.h',
         'output/bsp_walk_action.cc',
         'output/bsp_walk_action.h',
         'output/compositor_frame.cc',
         'output/compositor_frame.h',
         'output/compositor_frame_ack.cc',
         'output/compositor_frame_ack.h',
@@ skipping 358 matching lines @@
         'surfaces/surface_resource_holder.cc',
         'surfaces/surface_resource_holder.h',
         'surfaces/surfaces_export.h',
       ],
       'includes': [
         '../build/android/increase_size_for_speed.gypi',
       ],
     },
   ],
 }