Crash in RawResource::responseReceived() on successful revalidation.

BUG=247778
TEST=RawResourceTest.RevalidationSucceeded

Review URL: https://codereview.chromium.org/103123003

git-svn-id: svn://svn.chromium.org/blink/trunk@163882 bbb929c8-8fbe-4397-9dbb-9b2b20218538