Set last stack bounds to avoid updating the unchanged state

In the case of rotating camera to landscape, it reduces 25 times
unnecessary post.

Also removed unused PhoneWindowManager's ScreenshotHelper that
was migrated into DisplayPolicy.

Bug: 129389526
Test: go/wm-smoke

Change-Id: Idc3fb7ba7a4258ba69e2d97ed152db012c0e5cfa