NetS13nServiceWorker: More instrumentation for AppCache crash.

Based on the logs, it appears default_request_handler_factory_ is being
run on a URLLoaderRequestController before Start() was called.

My theory is that MaybeStartLoader is being called on the wrong object,
i.e., started_ is not yet set to true. Or maybe threading is
just wrong.

Bug: 857005
Change-Id: I4c918aba7ed489a071b02dfed5a9287f4063bfbf
Reviewed-on: https://chromium-review.googlesource.com/1127500
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572909}
3 files changed