Add support for websocket PING and PONG frames
Add support for websocket PING and PONG frames

The handling of control frames have been refactored to uniformly
hanlde CLOSE, PING and PONG frames.

Currently this is not tested as I have bot found a good way to test it
yet. It has been somewhat tested with a browser client forcing ping
messages from the server and processing the pong responses from the
browser.

R=ager@google.com, ajohnsen@google.com

BUG=none
TEST=none

Review URL: https://chromiumcodereview.appspot.com//10392195

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@7844 260f80e4-7a28-3924-810f-c04153c831b5

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