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This CL implements the infrastructure for logging PrinterEventProtos. Only
removals are logged right now.  Successful setup and setup abandonment will
be added in follow up CLs.

Bug: 647283
Change-Id: I9b3dbd37ee0db486d1c55686f729f65009d03cb8
Reviewed-on: https://chromium-review.googlesource.com/590584
Commit-Queue: Sean Kau <skau@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491222}