Add core plumbing for Instant Extended work

chrome/browser/ui/search/search_delegate.h

Index: chrome/browser/ui/search/search_delegate.h
diff --git a/chrome/browser/ui/search/search_delegate.h b/chrome/browser/ui/search/search_delegate.h
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+++ b/chrome/browser/ui/search/search_delegate.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_DELEGATE_H_
+#define CHROME_BROWSER_UI_SEARCH_SEARCH_DELEGATE_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "chrome/browser/ui/search/search_model_observer.h"
+
+class TabContents;
+
+namespace chrome {
+namespace search {
+
+class SearchModel;
+
+// The SearchDelegate class acts as a helper to the Browser class.
+// It is responsible for routing the changes from the active tab's
+// SearchModel through to the toolbar, tabstrip and other UI
+// observers.
+// Changes are propagated from the active tab's model via this class to the
+// Browser-level model.
+class SearchDelegate : public SearchModelObserver {
+ public:
+  explicit SearchDelegate(SearchModel* model);
+  virtual ~SearchDelegate();
+
+  // Overrides for SearchModelObserver:
+  virtual void ModeChanged(const Mode& mode) OVERRIDE;
+
+  // When the active tab is changed, the model state of this new active tab is
+  // propagated to the browser.
+  void OnTabActivated(TabContents* contents);
+
+  // When a tab is deactivated, this class no longer observes changes to the
+  // tab's model.
+  void OnTabDeactivated(TabContents* contents);
+
+  // When a tab is dettached, this class no longer observes changes to the
+  // tab's model.
+  void OnTabDetached(TabContents* contents);
+
+ private:
+  // Stop observing tab.
+  void StopObserveringTab(TabContents* contents);
+
+  // Weak.  The Browser class owns this.  The active |tab_model_| state is
+  // propagated to the |browser_model_|.
+  SearchModel* browser_model_;
+
+  // Weak.  The TabContents owns this.  It is the model of the active
+  // tab.  Changes to this model are propagated through to the |browser_model_|.
+  SearchModel* tab_model_;
+
+  DISALLOW_COPY_AND_ASSIGN(SearchDelegate);
+};
+
+}  // namespace search
+}  // namespace chrome
+
+#endif  // CHROME_BROWSER_UI_SEARCH_SEARCH_DELEGATE_H_