Make the various platform implementations of several OmniboxEditController
functions identical in preparation for hoisting them out of platform-specific
code.

BUG=none
TEST=none
R=sky@chromium.org

Review URL: https://codereview.chromium.org/25958002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227073 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227073