Move LayoutAndPaintAsyncThen to a separate compilation unit.

components/test_runner/test_runner.gyp

 # Copyright 2015 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': {
     # This turns on e.g. the filename-based detection of which
     # platforms to include source files on (e.g. files ending in
     # _mac.h or _mac.cc are only compiled on MacOSX).
     'chromium_code': 1,
@@ skipping 33 matching lines @@
         'accessibility_controller.cc',
         'accessibility_controller.h',
         'app_banner_client.cc',
         'app_banner_client.h',
         'event_sender.cc',
         'event_sender.h',
         'gamepad_controller.cc',
         'gamepad_controller.h',
         'gc_controller.cc',
         'gc_controller.h',
+        'layout_and_paint_async_then.cc',
+        'layout_and_paint_async_then.h',
         'layout_dump.cc',
         'layout_dump.h',
         'layout_test_runtime_flags.cc',
         'layout_test_runtime_flags.h',
         'mock_color_chooser.cc',
         'mock_color_chooser.h',
         'mock_content_settings_client.cc',
         'mock_content_settings_client.h',
         'mock_credential_manager_client.cc',
         'mock_credential_manager_client.h',
@@ skipping 141 matching lines @@
                   '$(SDKROOT)/System/Library/Frameworks/AppKit.framework',
                 ],
               },
             }],
           ],
         },
       ],
     }],  # OS=="mac" or OS=="win"
   ]
 }