Adds support for the search key in the Virtual Keyboard. We currently do not use the search key, but may need it in future layouts.

BUG=315071

Review URL: https://codereview.chromium.org/59813004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235803 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235803