Only matters if the simplified-fullscreen-ui flag is enabled.

After 15 minutes of no user input, the fullscreen / pointer lock bubble
is re-shown on the next user input. Previously, this only considered
mouse movement and key presses. Now all mouse events are also included
for both extending the 15-minute timer, and re-showing the bubble after
the timer has elapsed.

Importantly, this works while mouselock is active (otherwise, you would
not be reminded that you are in fullscreen if it also locks the mouse).
The way mouse events are propagated from the RenderWidgetHostViewAura to
the browser was changed to support this.

Re-land (CL was committed in r369300, reverted in r369549).

BUG=352425, 577983

Review URL: https://codereview.chromium.org/1561963003

Cr-Commit-Position: refs/heads/master@{#376357}