Move TextInputController from CppBoundClass to gin::Wrappable.

Also, change the class to use chromium coding style.

BUG=297480, 331301
R=jochen@chromium.org

Review URL: https://codereview.chromium.org/144013010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251692 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251692