Implement input.ime.sendKeyEvents and its browsertest.

BUG=326931

Review URL: https://codereview.chromium.org/110513004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241873 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241873