Don't inject chromevox content script in its own background page.

Apart from being unnecessary, this also causes us to have two connections
from each content script instance to the background page, which interferes
with some other changes I am working on.

R=dtseng@chromium.org, zelidrag@chromium.org
BUG=310285
TEST=manual: chromevox works as expected including in its own options page.

Review URL: https://codereview.chromium.org/141053010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246197 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246197
[GCM] Reland: Introduce GCMClientFactory to create GCMClient for GCMProfileService

We used to call GCMClient::Get() to get the single instance. This did not
work when we need to pass some initialization data from browser to it.
GCMClientFactory is introduced such that GCMClient instance can be
created, initialized and used in GCMProfileService::IOWorker.

BUG=284553
TEST=existing tests

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=245447

Review URL: https://codereview.chromium.org/135903005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246198 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246198