Do not advance mLastEventTime when enabling or disabling user activity.

Fixes a race condition between the keyguard and power key that sometimes resulted
in the power key failing to turn off the screen.

Fixes bug b/2212852 (Power button does not put phone to sleep)

Change-Id: I92498c5fddf2bfc32b105ea1a7ea14a06d83888e
Signed-off-by: Mike Lockwood <lockwood@android.com>

services/java/com/android/server/PowerManagerService.java

@@ -2079,7 +2079,6 @@ class PowerManagerService extends IPowerManager.Stub
     public void enableUserActivity(boolean enabled) {
         synchronized (mLocks) {
             mUserActivityAllowed = enabled;
-            mLastEventTime = SystemClock.uptimeMillis(); // we might need to pass this in
         }
     }