Always send module events to the ModuleDatabase on the UI thread.

Changes ModuleEventSinkImpl to take in a callback instead of
directly forwarding to the ModuleDatabase.

Bug: 943303
Change-Id: I23580fc1fe12d687ec945cb781e45fa8db82f958
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1529693
Commit-Queue: Patrick Monette <pmonette@chromium.org>
Reviewed-by: S├ębastien Marchand <sebmarchand@chromium.org>
Cr-Commit-Position: refs/heads/master@{#642730}
6 files changed