Added LatencyTimer to ease latency measurements

	new file:   core/java/android/os/LatencyTimer.java
	modified:   core/java/android/view/MotionEvent.java
	modified:   core/java/android/view/ViewRoot.java
	modified:   services/java/com/android/server/InputDevice.java
	modified:   services/java/com/android/server/KeyInputQueue.java
	modified:   services/java/com/android/server/WindowManagerService.java