GitLab

Adds a facility to stop touch events from being processed by all event
handlers and rewriters while the screen is off.

CastTouchEventGate is installed by the window manager as the first
event rewriter in the chain. When it is eanbled it will discard
all touch events, but notify registered observers that it has done so,
so the device can be woken up and touch event processing restored.

Bug: internal b/109894724
Test: unit test and manual on device
Change-Id: I82cf69d3d02f476256b28e2c3994b264fa31fc91
Reviewed-on: https://chromium-review.googlesource.com/1220166Reviewed-by: Alex Sakhartchouk <alexst@chromium.org>
Reviewed-by: Kevin Schoedel <kpschoedel@chromium.org>
Commit-Queue: Ryan Daum <rdaum@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590444}