Merge M54: "Implement base::PowerMonitor::IsOnBatteryPower() for OSX."

Merge M54: "Implement base::PowerMonitor::IsOnBatteryPower() for OSX."

For whatever reason this was never implemented; this is slimmed
down variant of the implementation in devices/battery/.

During this process I noticed the initial status for "is on
battery power" is incorrect. On Android, ChromeOS the initial
state is later supplied by Java and DBus respectively. On
Windows it was using a OneShotTimer. This replaces the Windows
implementation with a new protected setter which can be used
by the device source implementations to set the initial value
before a PowerMonitor exists.

BUG=649166
TEST=OSX properly detects battery changes. Initial state correct.

Review-Url: https://codereview.chromium.org/2351593004
Cr-Commit-Position: refs/heads/master@{#421350}
(cherry picked from commit 8621728865773df979e061a3b4ab5e6ef80a2cc2)

Committed: https://chromium.googlesource.com/chromium/src/+/dbfd5a68f50540765e6d485322e549a9575386bb

[DaleCurtis, 2016-09-29 22:07:10]

Description was changed from

==========
Merge M54: "Implement base::PowerMonitor::IsOnBatteryPower() for OSX."

For whatever reason this was never implemented; this is slimmed
down variant of the implementation in devices/battery/.

During this process I noticed the initial status for "is on
battery power" is incorrect. On Android, ChromeOS the initial
state is later supplied by Java and DBus respectively. On
Windows it was using a OneShotTimer. This replaces the Windows
implementation with a new protected setter which can be used
by the device source implementations to set the initial value
before a PowerMonitor exists.

BUG=649166
TEST=OSX properly detects battery changes. Initial state correct.

Review-Url: https://codereview.chromium.org/2351593004
Cr-Commit-Position: refs/heads/master@{#421350}
(cherry picked from commit 8621728865773df979e061a3b4ab5e6ef80a2cc2)
==========

to

==========
Merge M54: "Implement base::PowerMonitor::IsOnBatteryPower() for OSX."

For whatever reason this was never implemented; this is slimmed
down variant of the implementation in devices/battery/.

During this process I noticed the initial status for "is on
battery power" is incorrect. On Android, ChromeOS the initial
state is later supplied by Java and DBus respectively. On
Windows it was using a OneShotTimer. This replaces the Windows
implementation with a new protected setter which can be used
by the device source implementations to set the initial value
before a PowerMonitor exists.

BUG=649166
TEST=OSX properly detects battery changes. Initial state correct.

Review-Url: https://codereview.chromium.org/2351593004
Cr-Commit-Position: refs/heads/master@{#421350}
(cherry picked from commit 8621728865773df979e061a3b4ab5e6ef80a2cc2)

Committed:
https://chromium.googlesource.com/chromium/src/+/dbfd5a68f50540765e6d485322e5...
==========

[DaleCurtis, 2016-09-29 22:07:12]

Committed patchset #1 (id:1) manually as
dbfd5a68f50540765e6d485322e549a9575386bb.