ScriptRegexp::match(): gracefully fail if regexp.exec() throws.

Check if the internal v8 call to do the actual regexp matching threw
an exception and report that as a match failure.

R=haraken@chromium.org
BUG=377024

Review URL: https://codereview.chromium.org/300103002

git-svn-id: svn://svn.chromium.org/blink/trunk@174774 bbb929c8-8fbe-4397-9dbb-9b2b20218538