Provide skeleton for ChromeVox next.

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 1352 matching lines @@
 
     # Set to 1 to compile with the hole punching for the protected video.
     'video_hole%': 0,
 
     # Set to 1 to compile with MSE support for MPEG2 TS
     'enable_mpeg2ts_stream_parser%': 0,
 
     # Support ChromeOS touchpad gestures with ozone.
     'use_evdev_gestures%': 0,
 
+    # Whether to use the upcoming version of ChromeVox.

[dmazzoni, 2014/05/12 18:18:12]

Perhaps this should make it more clear that this "builds" ChromeVox Next, it
doesn't make Chrome "use" it unless you also enable a flag. Also, note that this
is Chrome OS only. How about:

# Chrome OS: whether to also build the upcoming version of
# ChromeVox, which can then be enabled via a command-line switch.
'build_chromevox_next%': 0,

[David Tseng, 2014/05/12 20:33:37]

Done.

+    'use_chromevox_next%': 0,
+
     'conditions': [
       # Enable the Syzygy optimization step for the official builds.
       ['OS=="win" and buildtype=="Official" and syzyasan!=1', {
         'syzygy_optimize%': 1,
       }, {
         'syzygy_optimize%': 0,
       }],
       # Get binutils version so we can enable debug fission if we can.
       ['os_posix==1 and OS!="mac" and OS!="ios"', {
         'conditions': [
@@ skipping 3861 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',
   },
 }