Handle TaskStackListener.onPinnedActivityRestartAttempt in PIP system UI

Bug: 26452296
Change-Id: Ic828462dce0b6f88c9b00fac36ade5492cec94fb
diff --git a/packages/SystemUI/src/com/android/systemui/tv/pip/PipManager.java b/packages/SystemUI/src/com/android/systemui/tv/pip/PipManager.java
index b237400..e947ed5 100644
--- a/packages/SystemUI/src/com/android/systemui/tv/pip/PipManager.java
+++ b/packages/SystemUI/src/com/android/systemui/tv/pip/PipManager.java
@@ -94,6 +94,12 @@
             }
         }
     };
+    private final Runnable mOnPinnedActivityRestartAttempt = new Runnable() {
+        @Override
+        public void run() {
+            movePipToFullscreen();
+        }
+    };
 
     private final BroadcastReceiver mBroadcastReceiver = new BroadcastReceiver() {
         @Override
@@ -315,6 +321,8 @@
 
         @Override
         public void onPinnedActivityRestartAttempt() {
+            // Post the message back to the UI thread.
+            mHandler.post(mOnPinnedActivityRestartAttempt);
         }
     }