Add more instrumentation for AppCache crash when S13nSW is enabled.

We expect the precreated AppCacheHost to exist in
AppCacheNavigationHandleCore once navigation starts on the IO thread.
But we know it doesn't exist at some point.  This CL add more logging to
try to narrow down possibilities of where the host was lost, if it was
ever created.

Bug: 857005
Change-Id: I0804b6dd972daf6e28e6ee5bf403e30b94df0b1a
Reviewed-on: https://chromium-review.googlesource.com/1125649
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572511}
3 files changed