Enable runtime switching between ChromeVox and ChromeVox next via command line.

chrome/browser/resources/chromeos/chromevox/generate_manifest.gypi

Index: chrome/browser/resources/chromeos/chromevox/generate_manifest.gypi
diff --git a/chrome/browser/resources/chromeos/chromevox/generate_manifest.gypi b/chrome/browser/resources/chromeos/chromevox/generate_manifest.gypi
index 3f94cb9d1ce3cb9f000ff4ce735b9032d44c37e9..e9dc0da59992c7ebcad1c969aa7fc10160da3750 100644
--- a/chrome/browser/resources/chromeos/chromevox/generate_manifest.gypi
+++ b/chrome/browser/resources/chromeos/chromevox/generate_manifest.gypi
@@ -19,6 +19,7 @@
     'generate_manifest_script_path': 'tools/generate_manifest.py',
     'is_guest_manifest%': 0,
     'key': 'MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDltVl1k15pjRzuZfMc3B69inxwm2bZeZ2O8/zFO+NluHnBm3GJ3fzdOoFGJd+M16I8p7zxxQyHeDMfWYASyCeB8XnUEDKjqNLQfCnncsANzHsYoEbYj2nEUML2P13b9q+AAvpCBpAJ4cZp81e9n1y/vbSXHE4385cgkKueItzikQIDAQAB',
+    'use_chromevox_next': 1,

[dmazzoni, 2014/09/22 06:36:28]

Can we just get rid of this from gyp rather than defining it to be 1 by default?
It's okay if you think there'd ever be a reason to compile it out.

[Peter Lundblad, 2014/09/22 09:00:46]

this means that all manifests generated will be for chromevox next (I patched
the CL and confirmed).  You need to add the % prefix to pick up the
value from the including context if set.  I also suggest defaulting to
0 for consistency.  So:
  'use_chromevox_next%': 0,

In addition, I'd rename this is_chromevox_next to be consistent with
is_guest_manifest because this is now not a build flag for whether to build
chromevox next at all, but rather a parameter to the manifest generation.

Also, please mention this variable in the file header as an optional
variable to be set before including this file.

[David Tseng, 2014/09/22 17:23:12]

Added comment and made this optional. Was still working on getting
use_chromevox_next to be entirely out of the build/common.gypi when messing
around with this.

   },
   'includes': [
     '../../../../../build/util/version.gypi',