Cleanup: Remove a no-op UTF16ToWideHack in Windows-only code.

Also do some misc cleanup while we are at it.

Review URL: https://codereview.chromium.org/77723012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236604 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236604