GitLab

These IPC extension messages are identical between chrome/chromecast.
Moving up to extensions/common

Bug: 837773
Test: Deploy ChromeOs manually (tidus)
Change-Id: I8884ea9726b69efb40c71614de11889bf01a2bb4
Reviewed-on: https://chromium-review.googlesource.com/c/1261976Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Randy Rossi <rmrossi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610442}