Remove PausableObjects from rtc peerconnection code.

RTCDataChannel used a timer to pause/resume. The timer is hooked up
to the kNetwork task queue which is the loading task queue.

Likewise the RTCPeerConnection object used a Async method runner which
wasn't necessary because it also uses the kNetwork task queue which
is pausable itself.

BUG=907125

Change-Id: I3cac8f9143aa4bfb7557f348cff052dc886b2c01
Reviewed-on: https://chromium-review.googlesource.com/c/1372224
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616355}
4 files changed