Add setBatteryStatusListener into Platform.

BUG=122593

Review URL: https://codereview.chromium.org/246773007

git-svn-id: svn://svn.chromium.org/blink/trunk@172419 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Un-skip XMLHttpRequest.send perf test

After further examination of the Nexus4 bot logs, I don't see any
recent crashes in this test. Tentatively re-enabling this test
to confirm that these particular crashes are gone.

BUG=353299
TBR=dtu@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/249073005

git-svn-id: svn://svn.chromium.org/blink/trunk@172420 bbb929c8-8fbe-4397-9dbb-9b2b20218538