Teach navigation throttles how to cancel requests in WillProcessResponse.

This is the first step towards moving various response-time checks up
from Blink into the browser. To support things like 'X-Frame-Options',
we'll need to do throttle checks after we can evaluate headers. This
patch starts us down that path by teaching NavigationHandleImpl,
NavigationResourceThrottle, and NavigationThrottle about response-time
checks. This patch shouldn't introduce any behavioral changes, as no
NavigationThrottle actually uses the new functionality yet.

BUG=555418
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_site_isolation

Review URL: https://codereview.chromium.org/1616943003

Cr-Commit-Position: refs/heads/master@{#372332}
6 files changed