Reland 166821 - Lazy initialization for ProcessesEventRouter.

Reland 166821 - Lazy initialization for ProcessesEventRouter. 
Using PKS::Shutdown this time.

Make it profile-scoped, not a singleton. 
Construct EventRouter at ExtensionSystem creation time. 
Implement EventRouter::Observer interface for lazy event router initialization, and use it for processes API. 

BUG=156715, 159265
TBR=ben@chromium.org


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=166872

[Yoyo Zhou, 2012-11-09 00:59:16]

The only changes from https://chromiumcodereview.appspot.com/11359081/ are in
ProcessesAPI:

- Unregister in Shutdown() instead of destructor.
- Lazily construct event router in the getter.

[Matt Perry, 2012-11-09 01:03:17]

lgtm

[commit-bot: I haz the power, 2012-11-09 01:13:08]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/yoz@chromium.org/11351004/1

[commit-bot: I haz the power, 2012-11-09 03:54:12]

Retried try job too often for step(s) browser_tests

[Yoyo Zhou, 2012-11-09 06:07:41]

+youngki FYI

[commit-bot: I haz the power, 2012-11-09 06:07:54]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/yoz@chromium.org/11351004/12003

[commit-bot: I haz the power, 2012-11-09 08:48:44]

Change committed as 166872

[Ben Goodger (Google), 2012-11-12 16:32:22]

lgtm for the gyp