Cloud Logging: Drop cached logs if a write timeout occurs.
Cloud Logging: Drop cached logs if a write timeout occurs.

BUG=skia:6246

Change-Id: I38ddf7c705b976297ca19e2d4705d1da17c2ca2d
Reviewed-on: https://skia-review.googlesource.com/8540
Commit-Queue: Joe Gregorio <b9cf2471ff6d33504cafe8e6f356b732b2cadced@google.com>
Reviewed-by: Ben Wagner <3ef7217be91069877d94f7907ce5479000772cd3@google.com>
Reviewed-by: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot