Calling start/stop listening in onStart/onStop

AppWidgetHost in N-MR1 was changed to make start/stop lisenting calls
light weight, which allows launcher to avoid getting unnecessary
updates when its not visible

Bug: 23892701
Change-Id: I1f40a1ddc51a9eee304e17e72106bc75afe6c1bc

src/com/android/launcher3/Launcher.java

@@ -950,6 +950,10 @@ public class Launcher extends Activity
         if (mLauncherCallbacks != null) {
             mLauncherCallbacks.onStop();
         }
+
+        if (Utilities.isNycMR1OrAbove()) {
+            mAppWidgetHost.stopListening();
+        }
     }
 
     @Override
@@ -960,6 +964,10 @@ public class Launcher extends Activity
         if (mLauncherCallbacks != null) {
             mLauncherCallbacks.onStart();
         }
+
+        if (Utilities.isNycMR1OrAbove()) {
+            mAppWidgetHost.startListening();
+        }
     }
 
     @Override

src/com/android/launcher3/LauncherAppWidgetHost.java

@@ -67,12 +67,6 @@ public class LauncherAppWidgetHost extends AppWidgetHost {
         }
     }
 
-    @Override
-    public void stopListening() {
-        super.stopListening();
-        clearViews();
-    }
-
     public void addProviderChangeListener(Runnable callback) {
         mProviderChangeListeners.add(callback);
     }