Revert "Fix to NullPointerException on move back in ActivityStack."

This reverts commit c6f060b6e0c21f5cfc632faab3bd66ca3d21f6e6.
Revert "BroadcastQueue: fix class typo of next receiver"

This reverts commit b645484a311d6172336a470814c17668e740e737.
Revert "Fix problem where PhoneWindowManager waits for keyguard to draw"

This reverts commit 9cdcea0ba9cf57d5b3a3472d106497ee8c471934.