Add a "Simplify Page" option to the print preview dialog

chrome/browser/ui/tab_helpers.h

 // Copyright 2014 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_TAB_HELPERS_H_
 #define CHROME_BROWSER_UI_TAB_HELPERS_H_
 
 namespace content {
 class WebContents;
 }
 
 namespace chrome {
 class BrowserTabStripModelDelegate;
 
 namespace android {
 class ChromeWebContentsDelegateAndroid;
 }
 }
 
 namespace prerender {
 class PrerenderContents;
 }
 
+class HiddenWebContents;
+
 // A "tab contents" is a WebContents that is used as a tab in a browser window
 // (or the equivalent on Android). The TabHelpers class allows specific classes
 // to attach the set of tab helpers that is used for tab contents.
 //
 // TODO(avi): This list is rather large, and for most callers it's due to the
 // fact that they need tab helpers attached early to deal with arbitrary
 // content loaded into a WebContents that will later be added to the tabstrip.
 // Is there a better way to handle this? (Ideally, this list would contain
 // only Browser and BrowserTabStripModelDelegate.)
 class TabHelpers {
  private:
   // Browser and its TabStripModelDelegate have intimate control of tabs.
   // TabAndroid is the equivalent on Android.
   friend class Browser;
   friend class chrome::BrowserTabStripModelDelegate;
 
   // These are the Android equivalents of the two classes above.
   friend class TabAndroid;
   friend class chrome::android::ChromeWebContentsDelegateAndroid;
 
   // chrome::Navigate creates WebContents that are destined for the tab strip,
   // and that might have WebUI that immediately calls back into random tab
   // helpers.
   friend class BrowserNavigatorWebContentsAdoption;
 
   // Prerendering loads pages that have arbitrary external content; it needs
   // the full set of tab helpers to deal with it.
   friend class prerender::PrerenderContents;
 
+  friend class HiddenWebContents;
+
   // Adopts the specified WebContents as a full-fledged browser tab, attaching
   // all the associated tab helpers that are needed for the WebContents to
   // serve in that role. It is safe to call this on a WebContents that was
   // already adopted.
   static void AttachTabHelpers(content::WebContents* web_contents);
 };
 
 #endif  // CHROME_BROWSER_UI_TAB_HELPERS_H_