Bug 1260519 - Support unsubscribing from Push API messages from a site. r=jchen

This was implemented, but never wired up.

I thought long and hard about how to unit test this, and it's quite
difficult.  First, we'd have to chose a layer of testing.  We could
unit test:

* the JS <-> Java message passing;

* the permission prompts <-> JS interface;

* some interactions with the Service Worker interface.

The first is difficult because none of our current testing emulators
have Google Play Services and GCM enabled, so we'd need to allow to
mock or otherwise fake the GCM registration.  Then we'd need to stand
up a mock autopush server (using httpd.js or the Java-side
equivalent), or mock out the autopush client as well.  At this point,
we're testing sendMessage.  This could be done, but I'd rather slide
this fix in before building out quite a bit of test infrastructure.
(For the record, the Java Push Service state machine is thoroughly
tested with Java unit tests, so I have confidence that the unsubscribe
logic works.)

The second is tested via the PushWebSocket tests, which are now
running on Android.  That is, if permissions and the PushService are
interacting badly, we should see it with the existing test suite.
Since PushServiceAndroidGCM is pretty much a pass-through, there's
little value to be added here.

Finally, the third is also tested via the PushWebSocket tests.
There's absolutely nothing GCM specific about the Service Worker
interface to the PushService.

So I'm left manually testing this -- and now we can unsubscribe from
Push messages from sites.

MozReview-Commit-ID: HiRiqasHJ27

--HG--
extra : rebase_source : ce01aa738d583a7200e9dc93ffa38dea9663779c
extra : amend_source : 03fc8a099e83871fa7bfe345168c063b69938d5e

mobile/android/base/java/org/mozilla/gecko/push/PushService.java

@@ -213,7 +213,7 @@ public class PushService implements BundleEventListener {
             if ("PushServiceAndroidGCM:Configure".equals(event)) {
                 final String endpoint = message.getString("endpoint");
                 if (endpoint == null) {
-                    Log.e(LOG_TAG, "endpoint must not be null in " + event);
+                    callback.sendError("endpoint must not be null in " + event);
                     return;
                 }
                 final boolean debug = message.getBoolean("debug", false);
@@ -222,6 +222,8 @@ public class PushService implements BundleEventListener {
                 return;
             }
             if ("PushServiceAndroidGCM:DumpRegistration".equals(event)) {
+                // In the future, this might be used to interrogate the Java Push Manager
+                // registration state from JavaScript.
                 callback.sendError("Not yet implemented!");
                 return;
             }
@@ -250,6 +252,10 @@ public class PushService implements BundleEventListener {
                 return;
             }
             if ("PushServiceAndroidGCM:UnregisterUserAgent".equals(event)) {
+                // In the future, this might be used to tell the Java Push Manager to unregister
+                // a User Agent entirely from JavaScript.  Right now, however, everything is
+                // subscription based; there's no concept of unregistering all subscriptions
+                // simultaneously.
                 callback.sendError("Not yet implemented!");
                 return;
             }
@@ -288,7 +294,20 @@ public class PushService implements BundleEventListener {
                 return;
             }
             if ("PushServiceAndroidGCM:UnsubscribeChannel".equals(event)) {
-                callback.sendError("Not yet implemented!");
+                final String channelID = message.getString("channelID");
+                if (channelID == null) {
+                    callback.sendError("channelID must not be null in " + event);
+                    return;
+                }
+
+                // Fire and forget.  See comments in the function itself.
+                final PushSubscription pushSubscription = pushManager.unsubscribeChannel(channelID);
+                if (pushSubscription != null) {
+                    callback.sendSuccess(null);
+                    return;
+                }
+
+                callback.sendError("Could not unsubscribe from channel: " + channelID);
                 return;
             }
         } catch (GcmTokenClient.NeedsGooglePlayServicesException e) {