Plumbing for screen pinning request from sysui

Removes lock-to-app request dialog from the AM.

Added a showScreenPinningRequest to IStatusBar to handle the
flow from app requesting lock task to showing the dialog.

This CL also allows startLockTaskOnCurrent (system|signature) to
start lock task directly.  (Note: this is the less locked version
that always allows exit through back + recents)

Bug: 16957435
Change-Id: I284918dd5989de6cb2767c2a717529eb5e9c6db4
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/tv/TvStatusBar.java b/packages/SystemUI/src/com/android/systemui/statusbar/tv/TvStatusBar.java
index 1b6a9e1..08732e5 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/tv/TvStatusBar.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/tv/TvStatusBar.java
@@ -178,4 +178,8 @@
     @Override
     public void onActivationReset(ActivatableNotificationView view) {
     }
+
+    @Override
+    public void showScreenPinningRequest() {
+    }
 }