Pausable Object Cleanup - PausableTask

Make PausableTask not inherit PausableTimer. There is no need
to schedule a timer since the kJavascriptTimer task queue already
is pausable. This class has no real user yet; Devlin claims that the
extension code will be using it soon.

BUG=907125

Change-Id: I270ef5d8e7f67c32d2377d8f8785ec56e941c204
Reviewed-on: https://chromium-review.googlesource.com/c/1378233
Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622083}
3 files changed