Revert 186925 since it breaks many of the builds on the bots (e.g.

build/common.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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 302 matching lines @@
 
       # Enable language detection.
       'enable_language_detection%': 1,
 
       # Enable printing support and UI.
       'enable_printing%': 1,
 
       # Webrtc compilation is enabled by default. Set to 0 to disable.
       'enable_webrtc%': 1,
 
+      # PPAPI by default does not support plugins making calls off the main
+      # thread. Set to 1 to turn on experimental support for out-of-process
+      # plugins to make call of the main thread.
+      'enable_pepper_threading%': 1,
+
       # Enables use of the session service, which is enabled by default.
       # Support for disabling depends on the platform.
       'enable_session_service%': 1,
 
       # Enables theme support, which is enabled by default.  Support for
       # disabling depends on the platform.
       'enable_themes%': 1,
 
       # Enables autofill dialog and associated features; disabled by default.
       'enable_autofill_dialog%' : 0,
@@ skipping 326 matching lines @@
     'use_ash%': '<(use_ash)',
     'use_openssl%': '<(use_openssl)',
     'use_nss%': '<(use_nss)',
     'os_bsd%': '<(os_bsd)',
     'os_posix%': '<(os_posix)',
     'use_glib%': '<(use_glib)',
     'toolkit_uses_gtk%': '<(toolkit_uses_gtk)',
     'use_x11%': '<(use_x11)',
     'use_gnome_keyring%': '<(use_gnome_keyring)',
     'linux_fpic%': '<(linux_fpic)',
+    'enable_pepper_threading%': '<(enable_pepper_threading)',
     'chromeos%': '<(chromeos)',
     'enable_viewport%': '<(enable_viewport)',
     'enable_hidpi%': '<(enable_hidpi)',
     'enable_touch_ui%': '<(enable_touch_ui)',
     'use_xi2_mt%':'<(use_xi2_mt)',
     'file_manager_extension%': '<(file_manager_extension)',
     'image_loader_extension%': '<(image_loader_extension)',
     'inside_chromium_build%': '<(inside_chromium_build)',
     'fastbuild%': '<(fastbuild)',
     'dcheck_always_on%': '<(dcheck_always_on)',
@@ skipping 1066 matching lines @@
       }],
       ['remoting==1', {
         'defines': ['ENABLE_REMOTING=1'],
       }],
       ['enable_webrtc==1', {
         'defines': ['ENABLE_WEBRTC=1'],
       }],
       ['proprietary_codecs==1', {
         'defines': ['USE_PROPRIETARY_CODECS'],
       }],
+      ['enable_pepper_threading==1', {
+        'defines': ['ENABLE_PEPPER_THREADING'],
+      }],
       ['enable_viewport==1', {
         'defines': ['ENABLE_VIEWPORT'],
       }],
       ['configuration_policy==1', {
         'defines': ['ENABLE_CONFIGURATION_POLICY'],
       }],
       ['input_speech==1', {
         'defines': ['ENABLE_INPUT_SPEECH'],
       }],
       ['notifications==1', {
@@ skipping 2335 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }