Revert "framework: fix reference leak in activiy manager"

This reverts commit c0a19bf19ebe2fd0de95965870a831be6488c7c4.
Revert "ActivityTrigger:  New class to invoke when activity starts/resumes"

This reverts commit 8f05289968ddb5f3736deb930c805f3cd6dbde16.

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