Revert "clear all recents button"

This reverts commit 72e841e576a127893cb7be77082193b6cf76bd01.
Clear all recents button based on PA commits

Conflicts:
	packages/SystemUI/src/com/android/systemui/recent/RecentsHorizontalScrollView.java
	packages/SystemUI/src/com/android/systemui/recent/RecentsPanelView.java