Restructure SDCH layering to allow more separation (observer/1->[0,n]

net/base/sdch_observer.h

+// Copyright 2014 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.
+
+// Observer interface for SDCH.  Observers can register with
+// the SdchManager to receive notifications of various SDCH events.
+
+#ifndef NET_BASE_SDCH_OBSERVER_H_
+#define NET_BASE_SDCH_OBSERVER_H_
+
+#include "net/base/net_export.h"
+
+class GURL;
+
+namespace net {
+
+class SdchManager;
+class URLRequest;
+
+class NET_EXPORT SdchObserver {
+ public:
+  // Notification that SDCH has seen a "Get-Dictionary" header.
+  virtual void OnGetDictionary(SdchManager* manager,

[Randy Smith (Not in Mondays), 2014/10/20 22:16:09]

Question for future CLs, not this one: I had originally tried to make this
notification pass a URLRequest, so that the fetching could be done in the
authentication context that resulted in the Get-Dictionary notification (wasn't
planning to do the authentication code, just to make it possible to do it in the
future).  But the notification went through SdchManager, which isn't by net/
internal layering allowed to know about URLRequests.  I tried to cheat by
leaving it an opaque type just passed by reference at the SdchManager interface,
but then sdch_manager_unittest.cc needed to know about it.  I tried to make it a
simple test jig in sdch_manager_unittest.cc, and got linking errors.  At that
point I threw up my hands, said "I don't need this functionality for this CL",
and decided to ask for advice.  Any ideas?

If I go truth&beauty on this, I say that indirecting the Get-Dictionary
notification through the SdchManager is a bit hacky because it's the storage
object, and the Get-Dictionary notification has nothing to do with storage.  But
that suggests creating another per-BrowserContext/Profile object in the SDCH
subsystem who's only purpose is to indirect that notification, and then I have
to figure out what directory it goes in and who owns it.  That struck me as ugly
too.  So at the moment I'm thinking that the right implementation is pretty much
what I tried to do above, and accept that the SdchManager unit tests need to
know about things that aren't appropriate to know in net/base, and that's
basically ok.  But you may well have better ideas.

+                               const GURL& request_url,
+                               const GURL& dictionary_url);
+
+  // Notification that SDCH has received a request to clear all
+  // its dictionaries.
+  virtual void OnClearDictionaries(SdchManager* manager);
+
+  virtual ~SdchObserver();
+  SdchObserver();
+
+ private:
+  // Reference count implementation to confirm no reference to
+  // this class is left on the SdchManager after class destruction.
+  friend class SdchManager;
+
+  void AddRef();
+  void RemoveRef();
+
+  int reference_count_;
+};
+
+}  // namespace net
+
+#endif  // NET_BASE_SDCH_MANAGER_H_