[IME API] Implement input view which reuses virtual keyboard window.

BUG=chromium:316524
TEST=Locally verified on sandbox of ChromeOS on Linux.

Review URL: https://codereview.chromium.org/91443002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237868 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237868