Fix print preview size calculation.

chrome/browser/ui/browser_window.h

 // Copyright 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_BROWSER_WINDOW_H_
 #define CHROME_BROWSER_UI_BROWSER_WINDOW_H_
 
 #include "base/callback_forward.h"
 #include "chrome/browser/lifetime/browser_close_manager.h"
 #include "chrome/browser/ui/bookmarks/bookmark_bar.h"
@@ skipping 304 matching lines @@
 #endif
 
   // Return the correct disposition for a popup window based on |bounds|.
   virtual WindowOpenDisposition GetDispositionForPopupBounds(
       const gfx::Rect& bounds) = 0;
 
   // Construct a FindBar implementation for the |browser|.
   virtual FindBar* CreateFindBar() = 0;
 
   // Return the WebContentsModalDialogHost for use in positioning web contents
-  // modal dialogs within the browser window.
+  // modal dialogs within the browser window. This can sometimes be NULL (for
+  // instance during tab drag on Views/Win32).
   virtual web_modal::WebContentsModalDialogHost*
       GetWebContentsModalDialogHost() = 0;
 
   // Invoked when the preferred size of the contents in current tab has been
   // changed. We might choose to update the window size to accomodate this
   // change.
   // Note that this won't be fired if we change tabs.
   virtual void UpdatePreferredSize(content::WebContents* web_contents,
                                    const gfx::Size& pref_size) {}
 
@@ skipping 62 matching lines @@
 
   // Returns the ToolbarView.
   virtual ToolbarView* GetToolbarView() const = 0;
 #endif
 
  protected:
   virtual ~BrowserWindowTesting() {}
 };
 
 #endif  // CHROME_BROWSER_UI_BROWSER_WINDOW_H_