Make SimpleEntryImpl ref counted.

net/disk_cache/simple/simple_index.h

Index: net/disk_cache/simple/simple_index.h
diff --git a/net/disk_cache/simple/simple_index.h b/net/disk_cache/simple/simple_index.h
index 76cf55ff5df6e51e09aad04bc60d82f0856624e6..44fdf1725f55d4c89a32e501d00bbadfd6c8c016 100644
--- a/net/disk_cache/simple/simple_index.h
+++ b/net/disk_cache/simple/simple_index.h
@@ -14,7 +14,7 @@
 #include "base/hash_tables.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 "base/time.h"
 #include "net/base/net_export.h"
 
@@ -67,15 +67,14 @@ class NET_EXPORT_PRIVATE EntryMetadata {
 
 // This class is not Thread-safe.
 class NET_EXPORT_PRIVATE SimpleIndex
-    : public base::SupportsWeakPtr<SimpleIndex> {
+    : public base::RefCountedThreadSafe<SimpleIndex> {
+  friend class base::RefCountedThreadSafe<SimpleIndex>;
  public:
   SimpleIndex(
       const scoped_refptr<base::TaskRunner>& cache_thread,
       const scoped_refptr<base::TaskRunner>& io_thread,
       const base::FilePath& path);
 
-  virtual ~SimpleIndex();
-
   void Initialize();
 
   void Insert(const std::string& key);
@@ -105,6 +104,8 @@ class NET_EXPORT_PRIVATE SimpleIndex
  private:
   typedef base::Callback<void(scoped_ptr<EntrySet>)> IndexCompletionCallback;
 
+  virtual ~SimpleIndex();
+
   static void LoadFromDisk(
       const base::FilePath& index_filename,
       const scoped_refptr<base::TaskRunner>& io_thread,