Use V8TRYCATCH_FOR_V8STRINGRESOURCE_VOID() in V8Window::openMethodCustom()

Use V8TRYCATCH_FOR_V8STRINGRESOURCE_VOID() in V8Window::openMethodCustom()
to that we properly abort (return early) if v8::String::ToString() returns
throws an exception.

R=haraken

Review URL: https://codereview.chromium.org/90243003

git-svn-id: svn://svn.chromium.org/blink/trunk@162765 bbb929c8-8fbe-4397-9dbb-9b2b20218538