arc-bridge: Enable ARC with a command-line flag

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 1545 matching lines @@
     'ozone_platform_headless%': 0,
 
     # Experiment: http://crbug.com/426914
     'envoy%': 0,
 
     # Used to set libjpeg_gyp_path. Chrome OS ui/gfx/gfx.gyp uses the IJG path
     # for robust login screen decoding.
     'libjpeg_ijg_gyp_path': '<(DEPTH)/third_party/libjpeg/libjpeg.gyp',
     'libjpeg_turbo_gyp_path': '<(DEPTH)/third_party/libjpeg_turbo/libjpeg.gyp',
 
-    # ARC instance disabled by default.
-    'enable_arc%': 0,
-
     'conditions': [
       ['buildtype=="Official"', {
         # Continue to embed build meta data in Official builds, basically the
         # time it was built.
         # TODO(maruel): This decision should be revisited because having an
         # official deterministic build has high value too but MSVC toolset can't
         # generate anything deterministic with WPO enabled AFAIK.
         'dont_embed_build_metadata%': 0,
       }],
       # Enable the Syzygy optimization step for the official builds.
@@ skipping 1520 matching lines @@
       ['<(use_nss_certs)==1 and >(nacl_untrusted_build)==0', {
         'defines': ['USE_NSS_CERTS=1'],
       }],
       ['<(chromeos)==1 and >(nacl_untrusted_build)==0', {
         'defines': ['OS_CHROMEOS=1'],
       }],
       ['enable_wexit_time_destructors==1 and OS!="win"', {
         # TODO: Enable on Windows too, http://crbug.com/404525
         'variables': { 'clang_warning_flags': ['-Wexit-time-destructors']},
       }],
-      ['<(enable_arc)==1', {
-        'defines': ['ENABLE_ARC=1'],
-      }],
       ['chromium_code==0', {
         'variables': {
           'clang_warning_flags': [
             # Lots of third-party libraries have unused variables. Instead of
             # suppressing them individually, we just blanket suppress them here.
             '-Wno-unused-variable',
           ],
         },
         'conditions': [
           [ 'os_posix==1 and OS!="mac" and OS!="ios"', {
@@ skipping 3255 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',
   },
 }