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

content/public/android/java/src/org/chromium/content/browser/BackgroundSyncNetworkObserver.java

Index: content/public/android/java/src/org/chromium/content/browser/BackgroundSyncNetworkObserver.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/BackgroundSyncNetworkObserver.java b/content/public/android/java/src/org/chromium/content/browser/BackgroundSyncNetworkObserver.java
new file mode 100644
index 0000000000000000000000000000000000000000..7dc74279f326d10a57e440dd06a9268db8c4e1d6
--- /dev/null
+++ b/content/public/android/java/src/org/chromium/content/browser/BackgroundSyncNetworkObserver.java
@@ -0,0 +1,58 @@
+// 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.
+
+package org.chromium.content.browser;
+
+import android.content.Context;
+
+import org.chromium.base.ThreadUtils;
+import org.chromium.base.annotations.CalledByNative;
+import org.chromium.base.annotations.JNINamespace;
+import org.chromium.base.annotations.NativeClassQualifiedName;
+import org.chromium.net.NetworkChangeNotifierAutoDetect;
+
+/**
+ * Contains the Java code used by the BackgroundSyncNetworkObserverAndroid C++ class.
+ *
+ * The purpose of this class is to listen for and forward network connectivity events to the
+ * BackgroundSyncNetworkObserverAndroid even when the application is paused. The standard

[Yaron, 2015/09/16 22:04:36]

I take it this works to have multiple registered NetworkChangeNotifierAutoDetect
instances with the same intent filter? Both of them get them the notification?

[iclelland, 2015/09/18 15:46:28]

It appears to, but it's not very clean. I'll see if I can make this a singleton
instead.

[Yaron, 2015/09/22 21:20:35]

Well you also aren't the only one to own an instance. NetworkChangeNotifier also
has one but I guess you've already verified it works. That was actually what I
was referring to. How do you get multiple observers? It seems like
BackgroundSyncManager constructor instantiates this so you'd have one per
instance of that. Oh you can have a BackgroundSyncManager per profile? I suppose
that's possible on Android with incognito.

+ * NetworkChangeNotifier does not listen for connectivity events when the application is paused.
+ *
+ * This class should live on the main thread.
+ */
+@JNINamespace("content")
+public class BackgroundSyncNetworkObserver implements NetworkChangeNotifierAutoDetect.Observer {

[Yaron, 2015/09/16 22:04:36]

nit: you can make this class and non-interface overrides private. Access
modifiers are just compile-time checks and we do JNI this way to indicate that
it's meant purely as a helper for native code.

[iclelland, 2015/09/18 15:46:28]

Thanks, done.

+
+    private NetworkChangeNotifierAutoDetect mNotifier;
+    private long mNativePtr;
+
+    public BackgroundSyncNetworkObserver(Context ctx, long nativePtr) {
+        mNotifier = new NetworkChangeNotifierAutoDetect(this, ctx, true);

[Yaron, 2015/09/16 22:04:36]

Hmm. You register this observer but never unregister it. If the native
counterpart were deleted, this object would still live because
NetworkChangeNotifierAutoDetect is still alive and it registers as a
BroadcastReceiver. If a notification were then to come through to the broadcast
receiver, you'd crash as soon as it calls into native. Is this possible? You'd
want to have @CalledByNative destroy method called from native destructor to
remedy this.

[iclelland, 2015/09/18 15:46:28]

Thanks -- I forgot about the additional reference that will keep this alive.
Switching to a singleton NCNAD means I'll need to unregister observers in any
case, so I'll add that.

+        mNativePtr = nativePtr;
+        ThreadUtils.runOnUiThread(new Runnable() {

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

This change, made necessary by the DCHECK_CURRENTLY_ON(UI) in
BackgroundSyncNetworkObserverAndroid::Observer::NotifyConnectionTypeChanged,
brings back the race that breaks the Incognito test.

(Because this runs on construction, we always notify the browser of the current
*actual* connectivity state, before we have a chance to override it in the test,
and sometimes that means that this online notification even happens *after* the
test override.)

+            @Override
+            public void run() {
+                    onConnectionTypeChanged(mNotifier.getCurrentConnectionType(

[Yaron, 2015/09/16 22:04:36]

nit: looks overidented (should be 4)

[iclelland, 2015/09/18 15:46:28]

Done.

+                            mNotifier.getCurrentNetworkState()));
+            }
+        });
+    }
+
+    @CalledByNative
+    public static BackgroundSyncNetworkObserver createObserver(Context ctx, long nativePtr) {
+        return new BackgroundSyncNetworkObserver(ctx, nativePtr);
+    }
+
+    @Override
+    public void onConnectionTypeChanged(int newConnectionType) {
+        nativeNotifyConnectionTypeChanged(mNativePtr, newConnectionType);
+    }
+
+    @Override
+    public void onMaxBandwidthChanged(double maxBandwidthMbps) {
+    }
+
+    @NativeClassQualifiedName("BackgroundSyncNetworkObserverAndroid::Observer")
+    private native void nativeNotifyConnectionTypeChanged(long nativePtr, int newConnectionType);
+}