wstring: remove wstring version of SplitString

Retry of r84336.

BUG=23581

Review URL: http://codereview.chromium.org/6930047

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@84355 0039d316-1c4b-4281-b951-d872f2087c98
void Label::OnMouseMoved(const MouseEvent& event) {
  UpdateContainsMouse(event);
}

void Label::OnMouseMoved(const MouseEvent& event) {
  UpdateContainsMouse(event);
}
