Cleanup: Stop creating RenderViewObservers from chrome/ in RenderViewer.

content/renderer/render_view_observer_tracker.h

+// Copyright (c) 2011 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.
+
+// Helper class used to find the RenderViewObservers for a given RenderView.
+//
+// Example usage:
+//
+//   class MyRVO : public RenderViewObserver,
+//                 public RenderViewObserverTracker<MyRVO> {
+//     ...
+//   };
+//
+//   RENDER_VIEW_OBSERVER_TRACKER_MAP(MyRVO);

[jam, 2011/04/05 18:10:07]

I like this approach a lot more, very nice :)

Can we get rid of the macro though?  i.e. have it as a static variable in
RenderViewObserverTracker's constructor?

[Lei Zhang, 2011/04/05 21:03:16]

I couldn't put it in the constructor, but I put it outside of the class and that
seems to work.

[jam, 2011/04/05 21:08:35]

wouldn't putting it in the header, outside any class, mean that a copy gets
created each time that file is included??

[Matt Perry, 2011/04/07 01:32:21]

Since it's declared as a static member in the class, there should still only be
1 instance. However, I would expect multiple definitions to be a link error.
Maybe only 1 file ever includes the headers where this macro is used? Or maybe
gcc is clever about merging the instances.

+//
+//   MyRVO::MyRVO(RenderView* render_view)
+//       : RenderViewObserver(render_view),
+//         RenderViewObserverTracker<SearchBox>(render_view) {
+//     ...
+//   }
+//
+//  void SomeFunction(RenderView* rv) {
+//    MyRVO* my_rvo = new MyRVO(rv);
+//    MyRVO* my_rvo_tracked = MyRVO::Get(rv);
+//    // my_rvo == my_rvo_tracked
+//  }
+
+#ifndef CONTENT_RENDERER_RENDER_VIEW_OBSERVER_TRACKER_H_
+#define CONTENT_RENDERER_RENDER_VIEW_OBSERVER_TRACKER_H_
+#pragma once
+
+#include <map>
+
+#include "base/lazy_instance.h"
+
+class RenderView;
+
+#define RENDER_VIEW_OBSERVER_TRACKER_MAP(ClassType) \
+    template <> \
+    base::LazyInstance<std::map<RenderView*, ClassType*> > \
+        RenderViewObserverTracker<ClassType>::render_view_map_( \
+            base::LINKER_INITIALIZED)
+
+template <class T>
+class RenderViewObserverTracker {
+ public:
+  static T* Get(RenderView* render_view) {
+    return render_view_map_.Get()[render_view];
+  }
+
+  explicit RenderViewObserverTracker(RenderView* render_view)
+      : render_view_(render_view) {
+    render_view_map_.Get()[render_view] = static_cast<T*>(this);
+  }
+  ~RenderViewObserverTracker() {
+    render_view_map_.Get().erase(render_view_);
+  }
+
+ private:
+  RenderView* render_view_;
+
+  static base::LazyInstance<std::map<RenderView*, T*> > render_view_map_;
+
+  DISALLOW_COPY_AND_ASSIGN(RenderViewObserverTracker<T>);
+};
+
+#endif  // CONTENT_RENDERER_RENDER_VIEW_OBSERVER_TRACKER_H_