Make Screen Orientation use Platform Events in order to handle polling.

Make Screen Orientation us Platform Events in order to handle polling.

BUG=162827
NOTRY=True

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=179620

[mlamouri (slow - plz ping), 2014-08-01 10:22:27]

Review ping. Adam, could you have a look at this CL. It follows
https://codereview.chromium.org/417213002/

As of https://codereview.chromium.org/417213002/, I will only land this if the
Blink API Owner meeting give a green light but I would like to have the patches
ready to land.

Thanks :)

[abarth-chromium, 2014-08-01 17:57:10]

LGTM

It's not clear to me whether we're calling notifyDispatcher() in exactly the
right places, but I don't see any specific bugs.  :)

[mlamouri (slow - plz ping), 2014-08-06 10:54:36]

The CQ bit was checked by mlamouri@chromium.org

[commit-bot: I haz the power, 2014-08-06 10:56:11]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/mlamouri@chromium.org/419643008/40001

[commit-bot: I haz the power, 2014-08-06 14:05:10]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  linux_blink_dbg on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_dbg/builds/2...)

[commit-bot: I haz the power, 2014-08-06 14:29:02]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-08-06 14:29:03]

Try jobs failed on following builders:
  linux_blink_dbg on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_dbg/builds/2...)

[mlamouri (slow - plz ping), 2014-08-06 14:44:17]

The CQ bit was checked by mlamouri@chromium.org

[commit-bot: I haz the power, 2014-08-06 14:45:07]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/mlamouri@chromium.org/419643008/40001

[commit-bot: I haz the power, 2014-08-06 15:19:54]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  linux_blink_dbg on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_dbg/builds/2...)

[mlamouri (slow - plz ping), 2014-08-06 15:30:40]

The CQ bit was unchecked by mlamouri@chromium.org

[mlamouri (slow - plz ping), 2014-08-06 15:30:41]

The CQ bit was checked by mlamouri@chromium.org

[commit-bot: I haz the power, 2014-08-06 15:30:52]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/mlamouri@chromium.org/419643008/40001

[commit-bot: I haz the power, 2014-08-06 15:31:54]

Change committed as 179620