Adds extension API for getting/observing input method.

API includes async input method getter and onChange event.

BUG=chromium-os:16735
TEST=InputMethodApiBasic browser_test

Review URL: http://codereview.chromium.org/7311005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@92493 0039d316-1c4b-4281-b951-d872f2087c98
20 files changed