Add gfx::Insets::ToString().

app/app_base.gypi

 # Copyright (c) 2009 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.
 
 {
   'target_defaults': {
     'variables': {
       'app_base_target': 0,
     },
     'target_conditions': [
@@ skipping 114 matching lines @@
         'gfx/font_util.h',
         'gfx/font_util.cc',
         'gfx/font_win.cc',
         'gfx/gdi_util.cc',
         'gfx/gdi_util.h',
         'gfx/gtk_util.cc',
         'gfx/gtk_util.h',
         'gfx/icon_util.cc',
         'gfx/icon_util.h',
         'gfx/insets.h',
+        'gfx/insets.cc',
         'gfx/native_widget_types.h',
         'gfx/native_widget_types_gtk.cc',
         'gfx/native_theme_win.cc',
         'gfx/native_theme_win.h',
         'gfx/gtk_native_view_id_manager.cc',
         'gfx/gtk_native_view_id_manager.h',
         'gfx/path.cc',
         'gfx/path_gtk.cc',
         'gfx/path_win.cc',
         'gfx/path.h',
@@ skipping 137 matching lines @@
           'configurations': {
             'Common': {
               'msvs_target_platform': 'x64',
             },
           },
         },
       ],
     }],
   ],
 }