Add Android's context menu handler used on the NTP.

chrome/browser/ui/webui/ntp/android/on_context_menu_item_selected_callback.h

Index: chrome/browser/ui/webui/ntp/android/on_context_menu_item_selected_callback.h
diff --git a/chrome/browser/ui/webui/ntp/android/on_context_menu_item_selected_callback.h b/chrome/browser/ui/webui/ntp/android/on_context_menu_item_selected_callback.h
new file mode 100644
index 0000000000000000000000000000000000000000..d7b82140027be803f87e06ea24a30fb8882e4660
--- /dev/null
+++ b/chrome/browser/ui/webui/ntp/android/on_context_menu_item_selected_callback.h
@@ -0,0 +1,41 @@
+// Copyright (c) 2012 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 CHROME_BROWSER_UI_WEBUI_NTP_ANDROID_ON_CONTEXT_MENU_ITEM_SELECTED_CALLBACK_H_
+#define CHROME_BROWSER_UI_WEBUI_NTP_ANDROID_ON_CONTEXT_MENU_ITEM_SELECTED_CALLBACK_H_
+
+#include "base/memory/ref_counted.h"
+
+class ContextMenuHandler;
+
+// This class is used by the ContextMenuHandler to create an intermediary object
+// as ContextMenuHandler is not RefCounted and therefore cannot be used in a
+// callback (and we cannot use an Unretained callback as we have no guarantee
+// that the ContextMenuHandler will outlive the callback).

[Evan Stade, 2012/08/22 00:24:51]

any reason not to use a weak pointer?

[Ted C, 2012/08/22 01:02:38]

Hmm...I didn't add this portion initially, so I'm not really sure.

Are you saying to pass a WeakPtr of the ContextMenuHandler (or some minimal
interface pulled out from that) instead of defining this separate class?  Seems
like other places in webui use that paradigm so I can certainly investigate that
here.

Just want to clarify before I start looking into that.

[Evan Stade, 2012/08/22 01:12:28]

yes, that's what I meant.

[Ted C, 2012/08/22 20:55:50]

Gave it a shot and seems to work just fine.

+class OnContextMenuItemSelectedCallBack
+    : public base::RefCounted<OnContextMenuItemSelectedCallBack> {
+ public:
+  explicit OnContextMenuItemSelectedCallBack(
+      ContextMenuHandler* context_menu_handler);
+
+  // Called by the object responsible for showing the menu when a menu is
+  // selected.
+  void ItemSelected(int item_id);
+
+  // Called by the ContextMenuHandler when its is destroyed so we can clear our
+  // reference to it.
+  void ClearContextMenuHandler();
+
+ private:
+  friend class base::RefCounted<OnContextMenuItemSelectedCallBack>;
+  ~OnContextMenuItemSelectedCallBack();
+
+  // Weak reference; we have a contract with this ContextMenuHandler to call our
+  // ClearContextMenuHander method when it becomes invalid.
+  ContextMenuHandler* context_menu_handler_;
+
+  DISALLOW_COPY_AND_ASSIGN(OnContextMenuItemSelectedCallBack);
+};
+
+#endif  // CHROME_BROWSER_UI_WEBUI_NTP_ANDROID_ON_CONTEXT_MENU_ITEM_SELECTED_CALLBACK_H_