Replace base::CallbackList with base::ObserverList in CastConfigDelegate

ash/cast_config_delegate.h

Index: ash/cast_config_delegate.h
diff --git a/ash/cast_config_delegate.h b/ash/cast_config_delegate.h
index 9c1e1c6b379e9e2312bcf3d1497ea8708c992480..d5eb6e9591f7bf60beccb8185470862237f9f570 100644
--- a/ash/cast_config_delegate.h
+++ b/ash/cast_config_delegate.h
@@ -10,7 +10,6 @@
 
 #include "ash/ash_export.h"
 #include "base/callback.h"

[achuithb, 2016/01/13 09:21:25]

Do you need this?

[jdufault, 2016/01/13 19:43:26]

Done.

-#include "base/callback_list.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string16.h"
@@ -71,12 +70,15 @@ class CastConfigDelegate {
     Activity activity;
   };
 
-  // The key is the receiver id.
   using ReceiversAndActivities = std::vector<ReceiverAndActivity>;
-  using ReceiversAndActivitesCallback =
-      base::Callback<void(const ReceiversAndActivities&)>;
-  using DeviceUpdateSubscription = scoped_ptr<
-      base::CallbackList<void(const ReceiversAndActivities&)>::Subscription>;
+
+  class ASH_EXPORT Observer {
+   public:
+    virtual ~Observer() {}

[achuithb, 2016/01/13 09:21:25]

I think this can be protected?

[jdufault, 2016/01/13 19:43:26]

Needs to be public so the extension API can call OnDevicesUpdated.

[stevenjb, 2016/01/13 20:02:18]

OnDevicesUpdated should be public, but the destructor should be protected.

[achuithb, 2016/01/13 21:08:33]

Yup, sorry I wasn't clear.

+
+    // Invoked whenever there is new receiver or activity information available.
+    virtual void OnDevicesUpdated(const ReceiversAndActivities& devices) = 0;
+  };

[achuithb, 2016/01/13 09:21:25]

DISALLOW_COPY_AND_ASSIGN perhaps?

[jdufault, 2016/01/13 19:43:26]

Doing so also requires defining a default constructor, which means that the
class is mostly boilerplate. I just looked at a couple of other observers and
they do not have DISALLOW_COPY_AND_ASSIGN.

The other observers have a protected dtor, so I've adjusted that.

[stevenjb, 2016/01/13 20:02:18]

It shouldn't. This is the preferred pattern:

class ASH_EXPORT Observer {
  public:
   virtual void OnDevicesUpdated(const ReceiversAndActivities& devices) = 0;

  protected:
   virtual ~Observer() {}

  private:
   DISALLOW_ASSIGN(NetworkConfigurationObserver);
};

[achuithb, 2016/01/13 21:08:33]

+1. Thanks for clarifying, Steven

[jdufault, 2016/01/13 22:02:23]

Done.

 
   virtual ~CastConfigDelegate() {}
 
@@ -85,10 +87,9 @@ class CastConfigDelegate {
   // gone. See crbug.com/551132.
   virtual bool HasCastExtension() const = 0;
 
-  // Adds a listener that will get invoked whenever the receivers or their
-  // associated activites have changed.
-  virtual DeviceUpdateSubscription RegisterDeviceUpdateObserver(
-      const ReceiversAndActivitesCallback& callback) = 0;
+  // Add or remove an observer.

[achuithb, 2016/01/13 09:21:25]

I feel like these administrative functions should be the last functions in this
class since they are the least interesting for readers of this file.

[jdufault, 2016/01/13 19:43:26]

Done.

+  virtual void AddObserver(Observer* observer) = 0;
+  virtual void RemoveObserver(Observer* observer) = 0;
 
   // Request fresh data from the backend. When the data is available, all
   // registered observers will get called.