Printing: Keep track of WebContents lifetime for the native printing UI.

chrome/browser/printing/printing_ui_web_contents_observer.h

+// Copyright 2013 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_PRINTING_PRINTING_UI_WEB_CONTENTS_OBSERVER_H_
+#define CHROME_BROWSER_PRINTING_PRINTING_UI_WEB_CONTENTS_OBSERVER_H_
+
+#include "base/basictypes.h"
+#include "content/public/browser/web_contents_observer.h"
+#include "ui/gfx/native_widget_types.h"
+
+// Wrapper used to keep track of the lifetime of a WebContents.
+// Lives on the UI thread.
+class PrintingUIWebContentsObserver : public content::WebContentsObserver {
+ public:
+  explicit PrintingUIWebContentsObserver(content::WebContents* web_contents);
+
+  // Return the parent NativeView of the observed WebContents.
+  gfx::NativeView GetParentView();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(PrintingUIWebContentsObserver);
+};
+
+#endif  // CHROME_BROWSER_PRINTING_PRINTING_UI_WEB_CONTENTS_OBSERVER_H_