Make SharedMemory track the size that was actually mapped

ui/surface/surface.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,
   },
 
   'target_defaults': {
@@ skipping 62 matching lines @@
         'accelerated_surface_win.cc',
         'accelerated_surface_win.h',
         'd3d9_utils_win.cc',
         'd3d9_utils_win.h',
         'io_surface_support_mac.cc',
         'io_surface_support_mac.h',
         'surface_export.h',
         'surface_switches.h',
         'surface_switches.cc',
         'transport_dib.h',
+        'transport_dib.cc',
         'transport_dib_android.cc',
         'transport_dib_linux.cc',
         'transport_dib_mac.cc',
         'transport_dib_win.cc',
       ],
       'defines': [
         'SURFACE_IMPLEMENTATION',
       ],
     },
   ],
@@ skipping 13 matching lines @@
             'surface',
           ],
           'sources': [
             'accelerated_surface_transformer_win_unittest.cc',
           ],
         },
       ],
     }],
   ],
 }