Fix memory leak in Launcher

Leak happened when a stack view was on the
workspace and then workspace forced a rebind of
its items (for example, when an app was installed)

Bug # 5629171

src/com/android/launcher2/Launcher.java

@@ -2920,6 +2920,7 @@ public void startBinding() {
             final CellLayout layoutParent = (CellLayout) workspace.getChildAt(i);
             layoutParent.removeAllViewsInLayout();
         }
+        mWidgetsToAdvance.clear();
         if (mHotseat != null) {
             mHotseat.resetLayout();
         }

src/com/android/launcher2/LauncherModel.java

@@ -176,12 +176,16 @@ private ArrayList<ItemInfo> unbindWorkspaceItemsOnMainThread() {
         // Ensure that we don't use the same workspace items data structure on the main thread
         // by making a copy of workspace items first.
         final ArrayList<ItemInfo> workspaceItems = new ArrayList<ItemInfo>(sWorkspaceItems);
+        final ArrayList<ItemInfo> appWidgets = new ArrayList<ItemInfo>(sAppWidgets);
         mHandler.post(new Runnable() {
             @Override
             public void run() {
                for (ItemInfo item : workspaceItems) {
                    item.unbind();
                }
+               for (ItemInfo item : appWidgets) {
+                   item.unbind();
+               }
             }
         });
 
@@ -1229,7 +1233,6 @@ public void run() {
                 }
             });
 
-            // Unbind previously bound workspace items to prevent a leak of AppWidgetHostViews.
             final ArrayList<ItemInfo> workspaceItems = unbindWorkspaceItemsOnMainThread();
 
             // Add the items to the workspace.