Make DETECT_IMPORTANT_CONTENT the default Plugins content setting based

chrome/chrome_browser.gypi

 # Copyright 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': {
     # All .cc, .h, .m, and .mm files under browser except for:
     # * tests and mocks.
     # * code below browser/chromeos
     # * code below browser/extensions
@@ skipping 1985 matching lines @@
       'browser/plugins/plugin_metadata.cc',
       'browser/plugins/plugin_metadata.h',
       'browser/plugins/plugin_observer.cc',
       'browser/plugins/plugin_observer.h',
       'browser/plugins/plugin_prefs.cc',
       'browser/plugins/plugin_prefs.h',
       'browser/plugins/plugin_prefs_factory.cc',
       'browser/plugins/plugin_prefs_factory.h',
       'browser/plugins/plugin_status_pref_setter.cc',
       'browser/plugins/plugin_status_pref_setter.h',
-      'browser/plugins/plugins_field_trial.cc',
-      'browser/plugins/plugins_field_trial.h',
       'browser/renderer_host/pepper/chrome_browser_pepper_host_factory.cc',
       'browser/renderer_host/pepper/chrome_browser_pepper_host_factory.h',
       'browser/renderer_host/pepper/device_id_fetcher.cc',
       'browser/renderer_host/pepper/device_id_fetcher.h',
       'browser/renderer_host/pepper/monitor_finder_mac.h',
       'browser/renderer_host/pepper/monitor_finder_mac.mm',
       'browser/renderer_host/pepper/pepper_broker_message_filter.cc',
       'browser/renderer_host/pepper/pepper_broker_message_filter.h',
       'browser/renderer_host/pepper/pepper_flash_browser_host.cc',
       'browser/renderer_host/pepper/pepper_flash_browser_host.h',
@@ skipping 1828 matching lines @@
           'variables': {
             'proto_in_dir': 'browser/sync_file_system/drive_backend',
             'proto_out_dir': 'chrome/browser/sync_file_system/drive_backend',
           },
           'includes': [ '../build/protoc.gypi' ]
         },
       ],
     },],
   ],
 }