[ServiceWorker] Add setURL() and url() to WebServiceWorkerResponse.

The renderer must know the original url of the result of the fetch event for CORS.

BUG=373120

Review URL: https://codereview.chromium.org/370733002

git-svn-id: svn://svn.chromium.org/blink/trunk@177575 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add ScriptForbiddenScope to collectGarbage() and performPendingSweep()

ScriptForbiddenScope verifies that V8 is not invoked during a GC phase and a sweeping phase. The verification is done only in Debug builds, and we're planning to enable it in Release builds in the future.

BUG=340522

Review URL: https://codereview.chromium.org/374523002

git-svn-id: svn://svn.chromium.org/blink/trunk@177576 bbb929c8-8fbe-4397-9dbb-9b2b20218538