Adds RefCountedDeleteOnMessageLoop

RefCountedDeleteOnMessageLoop is similar to RefCountedThreadSafe, but guarantees that
the referenced object will be deleted on the specified loop.
The functionality is similar to content::DeleteOnThread<> but does not depend on
BrowserThread.

The CL includes an example use of the class.

BUG=248049
TBR=stuartmorgan, joth

Review URL: https://chromiumcodereview.appspot.com/16938006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@206445 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 70 insertions, 0 deletions

diff --git a/base/memory/ref_counted_delete_on_message_loop.h b/base/memory/ref_counted_delete_on_message_loop.h
new file mode 100644
index 0000000..4527f16
--- /dev/null
+++ b/base/memory/ref_counted_delete_on_message_loop.h
@@ -0,0 +1,70 @@
+// Copyright 2013 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.
+
+#ifndef BASE_MEMORY_REF_COUNTED_DELETE_ON_MESSAGE_LOOP_H_
+#define BASE_MEMORY_REF_COUNTED_DELETE_ON_MESSAGE_LOOP_H_
+
+#include "base/location.h"
+#include "base/logging.h"
+#include "base/memory/ref_counted.h"
+#include "base/message_loop/message_loop_proxy.h"
+
+namespace base {
+
+// RefCountedDeleteOnMessageLoop is similar to RefCountedThreadSafe, and ensures
+// that the object will be deleted on a specified message loop.
+//
+// Sample usage:
+// class Foo : public RefCountedDeleteOnMessageLoop<Foo> {
+//
+//   Foo(const scoped_refptr<MessageLoopProxy>& loop)
+//       : RefCountedDeleteOnMessageLoop<Foo>(loop) {
+//     ...
+//   }
+//   ...
+//  private:
+//   friend class RefCountedDeleteOnMessageLoop<Foo>;
+//   friend class DeleteHelper<Foo>;
+//
+//   ~Foo();
+// };
+
+template <class T>
+class RefCountedDeleteOnMessageLoop : public subtle::RefCountedThreadSafeBase {
+ public:
+  RefCountedDeleteOnMessageLoop(
+      const scoped_refptr<MessageLoopProxy>& proxy) : proxy_(proxy) {
+    DCHECK(proxy_);
+  }
+
+  void AddRef() const {
+    subtle::RefCountedThreadSafeBase::AddRef();
+  }
+
+  void Release() const {
+    if (subtle::RefCountedThreadSafeBase::Release())
+      DestructOnMessageLoop();
+  }
+
+ protected:
+  friend class DeleteHelper<RefCountedDeleteOnMessageLoop>;
+  ~RefCountedDeleteOnMessageLoop() {}
+
+  void DestructOnMessageLoop() const {
+    const T* t = static_cast<const T*>(this);
+    if (proxy_->BelongsToCurrentThread())
+      delete t;
+    else
+      proxy_->DeleteSoon(FROM_HERE, t);
+  }
+
+  scoped_refptr<MessageLoopProxy> proxy_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(RefCountedDeleteOnMessageLoop);
+};
+
+}  // namespace base
+
+#endif  // BASE_MEMORY_REF_COUNTED_DELETE_ON_MESSAGE_LOOP_H_