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This change adds functionality to support lock screen notifications for
Android. The wake lock module now listens to dark resume notifications
from the power manager. It -

1. Starts a timer to check for partial wake locks acquired by Android.

2. After the timer in 1 expires, if no partial wake lock is acquired the
power manager is requested to re-suspend the system. If a partial wake
lock is acquired, then another hard timeout timer is set and also an
observer to wake lock release is set.

3. If wake lock is released, the system is re-suspended immediately.

4. If a wake lock is still acquired but the hard timeout expires then
the system is re-suspended immediately.

5. If the system transitions to a full resume all dark resume related
state and timers are cleared.

BUG=chromium:898297
TEST=Unit tests and end to end test with Android applications.

Change-Id: I6dbae0c5f63af67637032b62d0c56cae27d08bad
Reviewed-on: https://chromium-review.googlesource.com/c/1297474
Commit-Queue: Abhishek Bhardwaj <abhishekbh@chromium.org>
Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602980}