implement SetWatchEvent and WaitForEvent for trace-based-tests

chrome/chrome_tests.gypi

 # 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' : {
     'pyautolib_sources': [
       'app/chrome_command_ids.h',
       'app/chrome_dll_resource.h',
       'common/automation_constants.h',
       'common/pref_names.cc',
@@ skipping 3061 matching lines @@
         'renderer/safe_browsing/phishing_classifier_delegate_browsertest.cc',
         'renderer/safe_browsing/phishing_dom_feature_extractor_browsertest.cc',
         'renderer/safe_browsing/phishing_thumbnailer_browsertest.cc',
         'renderer/translate_helper_browsertest.cc',
         'renderer/webview_animating_overlay_browsertest.cc',
         'test/base/empty_browser_test.cc',
         'test/base/in_process_browser_test_browsertest.cc',
         'test/base/chrome_render_view_test.cc',
         'test/base/chrome_render_view_test.h',
         'test/base/chrome_test_launcher.cc',
+        'test/base/tracing_browsertest.cc',
         'test/data/webui/assertions.js',
         'test/data/webui/async_gen.cc',
         'test/data/webui/async_gen.h',
         'test/data/webui/async_gen.js',
         'test/data/webui/certificate_viewer_dialog_test.js',
         'test/data/webui/certificate_viewer_ui_test-inl.h',
         'test/data/webui/chrome_send_browsertest.cc',
         'test/data/webui/chrome_send_browsertest.h',
         'test/data/webui/chrome_send_browsertest.js',
         'test/data/webui/mock4js_browsertest.js',
@@ skipping 1660 matching lines @@
                 '--result', '<@(_outputs)',
                 '--isolate', 'browser_tests.isolate',
               ],
             },
           ],
         },
       ],
     }],
   ],  # 'conditions'
 }