Adds support for showing the match preview on views. It's behind the

chrome/browser/tab_contents/match_preview.h

+// Copyright (c) 2010 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_TAB_CONTENTS_MATCH_PREVIEW_H_
+#define CHROME_BROWSER_TAB_CONTENTS_MATCH_PREVIEW_H_
+
+#include "base/basictypes.h"
+#include "base/scoped_ptr.h"
+#include "googleurl/src/gurl.h"
+
+class TabContents;
+
+// MatchPreview maintains a TabContents that is intended to give a preview of
+// a URL. MatchPreview is owned by TabContents.
+//
+// As the user types in the omnibox the LocationBar updates MatchPreview by
+// way of 'Update'. If the user does a gesture on the preview, say clicks a
+// link, the TabContentsDelegate of the hosting TabContents is notified with
+// CommitMatchPreview and the TabContents maintained by MatchPreview replaces
+// the current TabContents in the TabStripModel.
+//
+// At any time the TabContents maintained by MatchPreview may be destroyed by
+// way of 'DestroyPreviewContents'. Consumers of MatchPreview can detect the
+// preview TabContents was destroyed by observing TAB_CONTENTS_DESTROYED.
+//
+// Consumers of MatchPreview can detect a new TabContents was created by
+// MatchPreview by listening for MATCH_PREVIEW_TAB_CONTENTS_CREATED.
+class MatchPreview {
+ public:
+  explicit MatchPreview(TabContents* host);
+  ~MatchPreview();
+
+  // Is MatchPreview enabled?
+  static bool IsEnabled();
+
+  // Invoked as the user types in the omnibox with the url to navigate to.  If
+  // the url is empty and there is a preview TabContents it is destroyed. If url
+  // is non-empty and the preview TabContents has not been created it is
+  // created.
+  void Update(const GURL& url);
+
+  // Destroys the preview TabContents. Does nothing if the preview TabContents
+  // has not been created.
+  void DestroyPreviewContents();
+
+  // Invoked when the user does some gesture that should trigger making the
+  // current previewed page the permanent page.
+  void CommitCurrentPreview();
+
+  // Releases the preview TabContents passing ownership to the caller. This is
+  // intended to be called when the preview TabContents is committed.
+  TabContents* ReleasePreviewContents();
+
+  // The TabContents we're maintaining the preview for.
+  TabContents* host() { return host_; }
+
+  // The preview TabContents; may be null.
+  TabContents* preview_contents() { return preview_contents_.get(); }
+
+ private:
+  class TabContentsDelegateImpl;
+
+  // The url we're displaying.
+  GURL url_;
+
+  // The TabContents we're providing the preview for.
+  TabContents* host_;
+
+  // Delegate of the preview TabContents. Used to detect when the user does some
+  // gesture on the TabContents and the preview needs to be activated.
+  scoped_ptr<TabContentsDelegateImpl> delegate_;
+
+  // The preview TabContents; may be null.
+  scoped_ptr<TabContents> preview_contents_;
+
+  DISALLOW_COPY_AND_ASSIGN(MatchPreview);
+};
+
+#endif  // CHROME_BROWSER_TAB_CONTENTS_MATCH_PREVIEW_H_