Adapt String::find method via StringUtil adapter.

This is needed to insulate generated code from blink::protocol namespace
from naming changes that we plan to do in the Great Blink Rename (which
in particular will rename wtf::StringBuilder::find method into Find).

BUG=683447
R=dgozman@chromium.org

Review-Url: https://codereview.chromium.org/2674583003 .
1 file changed