contacts: Add ContactManagerInterface::GetWeakPtr().

chrome/browser/chromeos/contacts/contact_manager.h

Index: chrome/browser/chromeos/contacts/contact_manager.h
diff --git a/chrome/browser/chromeos/contacts/contact_manager.h b/chrome/browser/chromeos/contacts/contact_manager.h
index 8f3d162c9b1b5d4f42359d708b26a2815c73394b..0e508ff41bca8f4052c113bbb23f905ebd900c4e 100644
--- a/chrome/browser/chromeos/contacts/contact_manager.h
+++ b/chrome/browser/chromeos/contacts/contact_manager.h
@@ -11,6 +11,7 @@
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "base/stl_util.h"
 #include "chrome/browser/chromeos/contacts/contact_store_observer.h"
@@ -34,6 +35,9 @@ class ContactManagerInterface {
   ContactManagerInterface() {}
   virtual ~ContactManagerInterface() {}
 
+  // Returns a weak pointer tied to the lifetime of this object.
+  virtual base::WeakPtr<ContactManagerInterface> GetWeakPtr() = 0;

[satorux1, 2012/08/30 16:43:29]

This looks worrisome. I'm not sure if WeakPtr works nicely with derived classes.
There was a  thread about this topic:

[chromium-dev] Weak ptrs for derived types?

which I didn't follow. :~(

Could you educate me if use of WeakPtr in this way is acceptable or not.

[Daniel Erat, 2012/08/30 16:56:16]

Thanks for pointing out that thread!

The original question there appeared to be about declaring a
WeakPtrFactory<Base> in Base (i.e. ContactManagerInterface) but then using it
from within Derived (i.e. ContactManager, ContactManagerStub) to vend
WeakPtr<Derived> objects.  There's some discussion about whether WeakPtr<Base>
should be downcastable to WeakPtr<Derived>.

I think that my usage is different: I'm declaring an abstract method in Base
(ContactManagerInterface) that returns WeakPtr<Base>, but Derived
(ContactManager, ContactManagerStub) creates its own WeakPtrFactory<Base>, and
there's never a need to downcast WeakPtr<Base> to WeakPtr<Derived>.

+
   // Adds or removes an observer for changes to |profile|'s contacts.
   virtual void AddObserver(ContactManagerObserver* observer,
                            Profile* profile) = 0;
@@ -71,6 +75,7 @@ class ContactManager : public ContactManagerInterface,
   void Init();
 
   // ContactManagerInterface overrides:
+  virtual base::WeakPtr<ContactManagerInterface> GetWeakPtr() OVERRIDE;
   virtual void AddObserver(ContactManagerObserver* observer,
                            Profile* profile) OVERRIDE;
   virtual void RemoveObserver(ContactManagerObserver* observer,
@@ -118,6 +123,10 @@ class ContactManager : public ContactManagerInterface,
   // Deletes values in |contact_stores_|.
   STLValueDeleter<ContactStoreMap> contact_stores_deleter_;
 
+  // Note: This should remain the last member so it'll be destroyed and
+  // invalidate its weak pointers before any other members are destroyed.
+  base::WeakPtrFactory<ContactManagerInterface> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(ContactManager);
 };