GCS Client: Handle error on Close() in SetFileContents
GCS Client: Handle error on Close() in SetFileContents

We had 403's which were logged but not handled because we weren't
checking the result of Close().

Bug: skia:
Change-Id: Ib10007d9e22c9a47d7489617988084f7781acb05
Reviewed-on: https://skia-review.googlesource.com/148061
Reviewed-by: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@google.com>
Commit-Queue: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@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