Migrate AwBrowserTerminator to taskscheduler

This requires removing the sequencing dependency between CrashDumpManager
and AwBrowserTerminator. Split minidump handling out from the child
process observation (now in ChildProcessCrashObserver), so that WebView
no longer requires two observers. AwBrowserTerminator now handles both
minidump processing (via CrashDumpManager) and renderer crash behaviour.

Bug: 689520
Change-Id: I3055536fba6e439d617039c48dacae7c389f2e2b
Reviewed-on: https://chromium-review.googlesource.com/582693
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Reviewed-by: Bo Liu <boliu@chromium.org>
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Reviewed-by: Alok Priyadarshi <alokp@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Commit-Queue: Tobias Sargeant <tobiasjs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#492675}
14 files changed