Enable to propagate fabricated key events to InputMethodEngine.

BUG=312218

Review URL: https://codereview.chromium.org/96313002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238043 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238043