Connect SimpleCache Backend active_entries_ more closely to Entry lifetime.

net/disk_cache/simple/simple_entry_impl.h

Index: net/disk_cache/simple/simple_entry_impl.h
diff --git a/net/disk_cache/simple/simple_entry_impl.h b/net/disk_cache/simple/simple_entry_impl.h
index 2d78d8bfe0a04c984916d9b09e3ee7d208855cd0..41f4cc142983b1b138442a6c046861e12306b9ab 100644
--- a/net/disk_cache/simple/simple_entry_impl.h
+++ b/net/disk_cache/simple/simple_entry_impl.h
@@ -11,7 +11,6 @@
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/memory/weak_ptr.h"
 #include "base/threading/thread_checker.h"
 #include "net/base/cache_type.h"
 #include "net/base/net_export.h"
@@ -40,8 +39,7 @@ struct SimpleEntryCreationResults;
 // disk cache. It proxies for the SimpleSynchronousEntry, which performs IO
 // on the worker thread.
 class NET_EXPORT_PRIVATE SimpleEntryImpl : public Entry,
-    public base::RefCounted<SimpleEntryImpl>,
-    public base::SupportsWeakPtr<SimpleEntryImpl> {
+    public base::RefCounted<SimpleEntryImpl> {
   friend class base::RefCounted<SimpleEntryImpl>;
  public:
   enum OperationsMode {
@@ -49,6 +47,14 @@ class NET_EXPORT_PRIVATE SimpleEntryImpl : public Entry,
     OPTIMISTIC_OPERATIONS,
   };
 
+  // The Backend can provide an instance of BackendDisconnector to an entry, to
+  // allow the entry to remove itself from the Backend for instance when doomed
+  // or destructed.
+  class BackendDisconnector {
+   public:
+    virtual ~BackendDisconnector() = 0;
+  };
+
   SimpleEntryImpl(net::CacheType cache_type,
                   const base::FilePath& path,
                   uint64 entry_hash,
@@ -56,6 +62,11 @@ class NET_EXPORT_PRIVATE SimpleEntryImpl : public Entry,
                   SimpleBackendImpl* backend,
                   net::NetLog* net_log);
 
+  // The provided |backend_disconnector| will be destroyed when this object
+  // no longer is to be managed by its backend.
+  void SetBackendDisconnector(
+      scoped_ptr<BackendDisconnector> backend_disconnector);
+
   // Adds another reader/writer to this entry, if possible, returning |this| to
   // |entry|.
   int OpenEntry(Entry** entry, const CompletionCallback& callback);
@@ -297,6 +308,10 @@ class NET_EXPORT_PRIVATE SimpleEntryImpl : public Entry,
                   int length,
                   int stream_index);
 
+  // The |backend_disconnector_| is among our first methods to insure that the

[Deprecated (see juliatuttle), 2014/08/22 19:26:38]

This is a field, not a method, and isn't destruction order the opposite of
construction order, so shouldn't it be near the *bottom* to be removed early?

[gavinp, 2014/08/25 13:18:27]

Removed this comment. And I think its placement is fine; I'm not moving it. It's
really scary referencing in to in-destruction objects, and putting this early in
destruction seems to encourage that kind of chicanery.

+  // entry removes itself from the backend early.
+  scoped_ptr<BackendDisconnector> backend_disconnector_;
+
   // All nonstatic SimpleEntryImpl methods should always be called on the IO
   // thread, in all cases. |io_thread_checker_| documents and enforces this.
   base::ThreadChecker io_thread_checker_;