Revert "ActivityTrigger:  New class to invoke when activity starts/resumes"

This reverts commit c3ff30d325407d8c7336eb3831e6d419eecd3c04.

Conflicts:
	core/jni/Android.mk
	core/jni/AndroidRuntime.cpp
	core/jni/com_android_internal_app_ActivityTrigger.cpp
	services/java/com/android/server/am/ActivityStack.java

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