Speculative revert did not stablize the tests... see crbug.com/149157

chrome/browser/extensions/system/system_api.h

Index: chrome/browser/extensions/system/system_api.h
===================================================================
--- chrome/browser/extensions/system/system_api.h	(revision 156892)
+++ chrome/browser/extensions/system/system_api.h	(working copy)
@@ -35,9 +35,16 @@
   virtual bool RunImpl() OVERRIDE;
 };
 
+// Dispatches systemPrivate.onBrightnessChanged event for extensions.
 void DispatchBrightnessChangedEvent(int brightness, bool user_initiated);
+
+// Dispatches systemPrivate.onVolumeChanged event for extensions.
 void DispatchVolumeChangedEvent(double volume, bool is_volume_muted);
+
+// Dispatches systemPrivate.onScreenChanged event for extensions.
 void DispatchScreenUnlockedEvent();
+
+// Dispatches systemPrivate.onWokeUp event for extensions.
 void DispatchWokeUpEvent();
 
 }  // namespace extensions