Fix print preview size calculation.

The size of the print preview should be based off of the available
area for dialogs, not the size of the web contents view.

BUG=

Review URL: https://chromiumcodereview.appspot.com/23460022

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@221957 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/ui/browser_window.h b/chrome/browser/ui/browser_window.h
index 39c2650..9158e95 100644
--- a/chrome/browser/ui/browser_window.h
+++ b/chrome/browser/ui/browser_window.h
@@ -322,7 +322,8 @@
   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;