GitLab

Implements LaunchCauseMetrics for launch types that don't involve
intents - Recents, Back, and Power button.

It's not possible to distinguish between Back and Recents in all cases.
However, when the Activity is killed in the background, and then
restored from Recents, Android adds a flag to the intent we can look
at. Also, when Chrome does not receive a UserLeaveHint when going to
the background, we can be sure that the Back button will not return
the user to that Chrome Activity.

We can detect resume by power button by looking at whether the
screen is off when Chrome is paused. (If Chrome happens to be killed
while the screen is off, the launcher is shown on screen on)

These changes range from extremely difficult to impossible to
integration test as you would need control of multiple apps for some,
and the ability to manipulate the Recents screen in others. I've opted
for unit testing here, and have manually tested every situation I could
think of in both CTA and CCT.

Bug: 1163961
Change-Id: I86a00dcf7333a22da724a1b26be2c5bcf5236cc3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2625909
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843898}