[BackgroundSync] init Android observer later

This change moves the initialization of
BackgroundSyncNetworkObserverAndroid to a later stage in the
BackgroundSyncManager startup. This avoids creating the
BackgroundSyncNetworkObserverAndroid::Observer instance
unnecessarily for WebView which does not support BackgroundSync.

Change-Id: I181ac886a336a4b32301a0b5790f1ed2963c4f2f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2052265Reviewed-by: Bo <boliu@chromium.org>
Reviewed-by: Mugdha Lakhani <nator@chromium.org>
Commit-Queue: Oksana Zhuravlova <oksamyt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#741660}

content/browser/android/background_sync_network_observer_android.cc

@@ -22,10 +22,6 @@ BackgroundSyncNetworkObserverAndroid::Observer::Create(
   DCHECK_CURRENTLY_ON(ServiceWorkerContext::GetCoreThreadId());
   scoped_refptr<BackgroundSyncNetworkObserverAndroid::Observer> observer(
       new BackgroundSyncNetworkObserverAndroid::Observer(callback));
-  RunOrPostTaskOnThread(
-      FROM_HERE, BrowserThread::UI,
-      base::BindOnce(&BackgroundSyncNetworkObserverAndroid::Observer::Init,
-                     observer));
   return observer;
 }
 
@@ -71,16 +67,27 @@ BackgroundSyncNetworkObserverAndroid::BackgroundSyncNetworkObserverAndroid(
     base::RepeatingClosure network_changed_callback)
     : BackgroundSyncNetworkObserver(std::move(network_changed_callback)) {
   DCHECK_CURRENTLY_ON(ServiceWorkerContext::GetCoreThreadId());
-
-  observer_ = Observer::Create(base::BindRepeating(
-      &BackgroundSyncNetworkObserverAndroid::OnConnectionChanged,
-      weak_ptr_factory_.GetWeakPtr()));
 }
 
 BackgroundSyncNetworkObserverAndroid::~BackgroundSyncNetworkObserverAndroid() {
   DCHECK_CURRENTLY_ON(ServiceWorkerContext::GetCoreThreadId());
 }
 
+void BackgroundSyncNetworkObserverAndroid::Init() {
+  DCHECK_CURRENTLY_ON(ServiceWorkerContext::GetCoreThreadId());
+  observer_ = Observer::Create(base::BindRepeating(
+      &BackgroundSyncNetworkObserverAndroid::OnConnectionChanged,
+      weak_ptr_factory_.GetWeakPtr()));
+  if (ServiceWorkerContext::IsServiceWorkerOnUIEnabled()) {
+    observer_->Init();
+  } else {
+    RunOrPostTaskOnThread(
+        FROM_HERE, BrowserThread::UI,
+        base::BindOnce(&BackgroundSyncNetworkObserverAndroid::Observer::Init,
+                       observer_));
+  }
+}
+
 void BackgroundSyncNetworkObserverAndroid::RegisterWithNetworkConnectionTracker(
     network::NetworkConnectionTracker* network_connection_tracker) {}
 

content/browser/android/background_sync_network_observer_android.h

@@ -30,6 +30,9 @@ class BackgroundSyncNetworkObserverAndroid
 
   ~BackgroundSyncNetworkObserverAndroid() override;
 
+  // Creates and initializes the Observer (below) instance.
+  void Init() override;
+
   // This class lives on the UI thread and mediates all access to the Java
   // BackgroundSyncNetworkObserver, which it creates and owns. It is in turn
   // owned by the BackgroundSyncNetworkObserverAndroid.
@@ -39,6 +42,7 @@ class BackgroundSyncNetworkObserverAndroid
    public:
     static scoped_refptr<BackgroundSyncNetworkObserverAndroid::Observer> Create(
         base::RepeatingCallback<void(network::mojom::ConnectionType)> callback);
+    void Init();
 
     // Called from BackgroundSyncNetworkObserver.java over JNI whenever the
     // connection type changes. This updates the current connection type seen by
@@ -56,7 +60,6 @@ class BackgroundSyncNetworkObserverAndroid
 
     explicit Observer(
         base::RepeatingCallback<void(network::mojom::ConnectionType)> callback);
-    void Init();
     ~Observer();
 
     // This callback is to be run on the IO thread whenever the connection type
@@ -71,7 +74,8 @@ class BackgroundSyncNetworkObserverAndroid
   void RegisterWithNetworkConnectionTracker(
       network::NetworkConnectionTracker* network_connection_tracker) override;
 
-  // Accessed on UI Thread
+  // Accessed on UI Thread.
+  // Null until Init() is called.
   scoped_refptr<Observer> observer_;
 
   base::WeakPtrFactory<BackgroundSyncNetworkObserverAndroid> weak_ptr_factory_{

content/browser/background_sync/background_sync_manager.cc

@@ -744,6 +744,8 @@ void BackgroundSyncManager::InitDidGetControllerParameters(
     return;
   }
 
+  network_observer_->Init();
+
   GetDataFromBackend(
       kBackgroundSyncUserDataKey,
       base::BindOnce(&BackgroundSyncManager::InitDidGetDataFromBackend,

content/browser/background_sync/background_sync_network_observer.h

@@ -24,6 +24,10 @@ class CONTENT_EXPORT BackgroundSyncNetworkObserver
 
   ~BackgroundSyncNetworkObserver() override;
 
+  // Does nothing in this class, but can be overridden to do some work
+  // separately from the constructor.
+  virtual void Init() {}
+
   // Enable or disable notifications coming from the NetworkConnectionTracker.
   // (For preventing flakes in tests)
   static void SetIgnoreNetworkChangesForTests(bool ignore);