Binding Taskbar directly from Launcher model

This allows taskbar to be loaded even in case of 3P Launchers
and removes dependency on LauncherActivity lifecycle

Bug: 187353581
Bug: 188788621
Test: Manual
Change-Id: I5a0988e0697b41677d4c58f0213aef14ec0c0972
diff --git a/src/com/android/launcher3/LauncherModel.java b/src/com/android/launcher3/LauncherModel.java
index eef3980..6966abf 100644
--- a/src/com/android/launcher3/LauncherModel.java
+++ b/src/com/android/launcher3/LauncherModel.java
@@ -144,9 +144,10 @@
         enqueueModelUpdateTask(new AddWorkspaceItemsTask(itemList));
     }
 
-    public ModelWriter getWriter(boolean hasVerticalHotseat, boolean verifyChanges) {
+    public ModelWriter getWriter(boolean hasVerticalHotseat, boolean verifyChanges,
+            @Nullable Callbacks owner) {
         return new ModelWriter(mApp.getContext(), this, mBgDataModel,
-                hasVerticalHotseat, verifyChanges);
+                hasVerticalHotseat, verifyChanges, owner);
     }
 
     @Override
@@ -329,7 +330,7 @@
     public boolean addCallbacksAndLoad(Callbacks callbacks) {
         synchronized (mLock) {
             addCallbacks(callbacks);
-            return startLoader();
+            return startLoader(new Callbacks[] { callbacks });
 
         }
     }
@@ -349,26 +350,32 @@
      * @return true if the page could be bound synchronously.
      */
     public boolean startLoader() {
+        return startLoader(new Callbacks[0]);
+    }
+
+    private boolean startLoader(Callbacks[] newCallbacks) {
         // Enable queue before starting loader. It will get disabled in Launcher#finishBindingItems
         ItemInstallQueue.INSTANCE.get(mApp.getContext())
                 .pauseModelPush(ItemInstallQueue.FLAG_LOADER_RUNNING);
         synchronized (mLock) {
-            // Don't bother to start the thread if we know it's not going to do anything
-            final Callbacks[] callbacksList = getCallbacks();
+            // If there is already one running, tell it to stop.
+            boolean wasRunning = stopLoader();
+            boolean bindDirectly = mModelLoaded && !mIsLoaderTaskRunning;
+            boolean bindAllCallbacks = wasRunning || !bindDirectly || newCallbacks.length == 0;
+            final Callbacks[] callbacksList = bindAllCallbacks ? getCallbacks() : newCallbacks;
+
             if (callbacksList.length > 0) {
                 // Clear any pending bind-runnables from the synchronized load process.
                 for (Callbacks cb : callbacksList) {
                     MAIN_EXECUTOR.execute(cb::clearPendingBinds);
                 }
 
-                // If there is already one running, tell it to stop.
-                stopLoader();
                 LoaderResults loaderResults = new LoaderResults(
                         mApp, mBgDataModel, mBgAllAppsList, callbacksList);
-                if (mModelLoaded && !mIsLoaderTaskRunning) {
+                if (bindDirectly) {
                     // Divide the set of loaded items into those that we are binding synchronously,
                     // and everything else that is to be bound normally (asynchronously).
-                    loaderResults.bindWorkspace();
+                    loaderResults.bindWorkspace(bindAllCallbacks);
                     // For now, continue posting the binding of AllApps as there are other
                     // issues that arise from that.
                     loaderResults.bindAllApps();
@@ -387,7 +394,7 @@
      * If there is already a loader task running, tell it to stop.
      * @return true if an existing loader was stopped.
      */
-    public boolean stopLoader() {
+    private boolean stopLoader() {
         synchronized (mLock) {
             LoaderTask oldTask = mLoaderTask;
             mLoaderTask = null;