Add core plumbing for Instant Extended work

chrome/browser/ui/search/search_model_observer_bridge.h

Index: chrome/browser/ui/search/search_model_observer_bridge.h
diff --git a/chrome/browser/ui/search/search_model_observer_bridge.h b/chrome/browser/ui/search/search_model_observer_bridge.h
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+// 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_SEARCH_SEARCH_MODEL_OBSERVER_BRIDGE_H_
+#define CHROME_BROWSER_UI_SEARCH_SEARCH_MODEL_OBSERVER_BRIDGE_H_
+#pragma once
+
+#include "chrome/browser/ui/search/search_model.h"
+#include "chrome/browser/ui/search/search_model_observer.h"
+
+namespace chrome {
+namespace search {
+
+template <class Receiver>
+class SearchModelObserverBridge : public SearchModelObserver {
+ public:
+  SearchModelObserverBridge(Receiver* receiver, SearchModel* model)
+      : receiver_(receiver),
+        model_(model) {
+    model_->AddObserver(this);
+  }
+
+  ~SearchModelObserverBridge() {
+    model_->RemoveObserver(this);
+  }
+
+  // SearchModelObserver:
+  virtual void ModeChanged(const Mode& mode) OVERRIDE {
+    [receiver_ modeChanged:mode];
+  }
+
+ private:
+  // Weak.  Owns us.
+  Receiver* receiver_;
+
+  // Weak.
+  SearchModel* model_;
+
+  DISALLOW_COPY_AND_ASSIGN(SearchModelObserverBridge);
+};
+
+}  // namespace search
+}  // namespace chrome
+
+#endif  // CHROME_BROWSER_UI_SEARCH_SEARCH_MODEL_OBSERVER_BRIDGE_H_