Remove calls of PrerenderTracker::TryCancelOnIOThread in PrerenderResourceThrottle and instead call PrerenderContents::Destroy directly on the UI thread.

This is part of the work on removing calls to ResourceRequestInfo::GetAssociatedRenderView. The last callers to that method are using it to cancel prerenders if they haven't been used yet, so the checking/cancelling needs to all move to the UI thread.

BUG=304341
R=davidben@chromium.org

Review URL: https://codereview.chromium.org/123753003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242955 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242955
[GCM] Add TTL support

TTL is currently enforced at Send time, resend time, and reconnect. It
does not take into account clock changes.

BUG=284553

Review URL: https://codereview.chromium.org/117513004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242956 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242956