Avoid persisting of QUIC server config information in Stable and Beta
channels.

Will delete this flag once we have implemented clearing of QUIC
server config information from clearing cookies dialog.

r=rch, eroman, sky, jar

Review URL: https://codereview.chromium.org/185083002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254562 0039d316-1c4b-4281-b951-d872f2087c98
Killing off QUICv12, including cleaning out all of the code for handling
headers within a stream.

Merge internal change: 62227108

R=rch@chromium.org

Review URL: https://codereview.chromium.org/185203003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254563 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254563
Avoid calling ThreadWatcherList::StartWatchingAll twice

Doing so causes an assert in the ThreadWatcherObserver constructor
and is anyway the wrong thing to do (should not start twice).

BUG=348072

Review URL: https://codereview.chromium.org/185713003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254564 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254564