GitLab

- Adds int32 and bool I/O into IBusObjectReader/Writer.
- Adds AppendIBusText and PopIBusText into IBusObjectReader/Writer
- Adds AppendStringAsIBusText and PopStringFromIBusText as utility function, because we frequently uses IBusText as a plain text in Chrome.

BUG=None
TEST=chromeos_unittests

Review URL: https://chromiumcodereview.appspot.com/10384141

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@138280 0039d316-1c4b-4281-b951-d872f2087c98