[BackgroundSync] Trigger Background Sync events when Chrome is backgrounded on Android

content/browser/android/background_sync_network_observer_android.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/browser/android/background_sync_network_observer_android.h"
+
+#include "jni/BackgroundSyncNetworkObserver_jni.h"
+
+namespace content {
+
+// static
+bool BackgroundSyncNetworkObserverAndroid::Observer::RegisterNetworkObserver(
+    JNIEnv* env) {
+  return RegisterNativesImpl(env);
+}
+
+BackgroundSyncNetworkObserverAndroid::Observer::Observer(
+    base::Callback<void(net::NetworkChangeNotifier::ConnectionType)> callback)
+    : callback_(callback) {

[jkarlin, 2015/09/16 17:39:44]

DCHECK on UI thread

[iclelland, 2015/09/16 19:14:16]

Done. Well, actually checks for IO thread now, since I'm constructing it there.

+  // Attach a Java BackgroundSyncNetworkObserver object. Its lifetime will be
+  // scoped to the lifetime of this object.
+  JNIEnv* env = base::android::AttachCurrentThread();
+  base::android::ScopedJavaLocalRef<jobject> obj =
+      Java_BackgroundSyncNetworkObserver_createObserver(
+          env, base::android::GetApplicationContext(),
+          reinterpret_cast<jlong>(this));
+  observer_ = obj;
+}
+
+void BackgroundSyncNetworkObserverAndroid::Observer::
+    NotifyConnectionTypeChanged(JNIEnv* env,
+                                jobject jcaller,
+                                jint new_connection_type) {

[jkarlin, 2015/09/16 17:39:44]

DCHECK on UI thread

[iclelland, 2015/09/16 19:14:16]

Done. See the corresponding change to the Java BackgroundSyncNetworkObserver
constructor to comply with this.

+  BrowserThread::PostTask(
+      BrowserThread::IO, FROM_HERE,
+      base::Bind(callback_,
+                 static_cast<net::NetworkChangeNotifier::ConnectionType>(
+                     new_connection_type)));
+}
+
+BackgroundSyncNetworkObserverAndroid::BackgroundSyncNetworkObserverAndroid(
+    const base::Closure& network_changed_callback)
+    : BackgroundSyncNetworkObserver(network_changed_callback),
+      weak_ptr_factory_(this) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+
+  // Remove the observer attached by the NetworkObserver constructor
+  net::NetworkChangeNotifier::RemoveNetworkChangeObserver(this);
+
+  BrowserThread::PostTask(
+      BrowserThread::UI, FROM_HERE,
+      base::Bind(
+          &BackgroundSyncNetworkObserverAndroid::InitializeOnUIThread,
+          weak_ptr_factory_.GetWeakPtr(),

[jkarlin, 2015/09/16 17:39:44]

You can't use a weakptr on a different thread.

Here is a common pattern:

Make BSNOA::Observer inherit from RefCountedThreadSafe and use the parameters to
make sure its destructor is called on the UI thread if the destructor isn't
thread safe.

Create the BSNOA::Observer on the IO thread.

[iclelland, 2015/09/16 17:47:38]

Right -- I didn't think I was, by doing it this way. I thought this code, which
ran on the IO thread, safely encapsulated the weakptr in the callback until it
was used to post back to the IO thread...

... and now I see the issue :) Thanks.
Already done, see the .h file.
That I will try. Thanks!

[iclelland, 2015/09/16 19:14:16]

Done.

+
+          base::Bind(&BackgroundSyncNetworkObserverAndroid::OnNetworkChanged,
+                     weak_ptr_factory_.GetWeakPtr())));
+}
+
+void BackgroundSyncNetworkObserverAndroid::InitializeOnUIThread(
+    base::Callback<void(net::NetworkChangeNotifier::ConnectionType)> callback) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  // Attach a native observer on the UI thread
+  observer_ = new Observer(callback);
+}
+
+BackgroundSyncNetworkObserverAndroid::~BackgroundSyncNetworkObserverAndroid() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+}
+}  // namespace content