Add CPU boosting hooks

 * Boost CPU to max during scrolling
 * Boost CPU to max on activity start/resume
 * Inspired by a patch from CodeAuora.

Conflicts:
	services/java/com/android/server/am/ActivityStack.java

Change-Id: I72f2c2851b01fbceabddead03a4c3a7a0526ca61
Merge "Add CPU boosting hooks" into jb4.3