Don't compile code for desktop zoom or GuestViews on mobile platforms.

chrome/browser/ui/prefs/prefs_tab_helper.h

 // Copyright (c) 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_PREFS_PREFS_TAB_HELPER_H_
 #define CHROME_BROWSER_UI_PREFS_PREFS_TAB_HELPER_H_
 
 #include "base/callback_list.h"
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
-#include "chrome/browser/ui/zoom/chrome_zoom_level_prefs.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/web_contents_user_data.h"
 
+#if !defined(OS_ANDROID)
+#include "chrome/browser/ui/zoom/chrome_zoom_level_prefs.h"
+#endif
+
 class Profile;
 
 namespace content {
 class WebContents;
 }
 
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
@@ skipping 26 matching lines @@
   void OnFontFamilyPrefChanged(const std::string& pref_name);
   void OnWebPrefChanged(const std::string& pref_name);
 
   void NotifyWebkitPreferencesChanged(const std::string& pref_name);
 
   content::WebContents* web_contents_;
   Profile* profile_;
   content::NotificationRegistrar registrar_;
   std::unique_ptr<base::CallbackList<void(void)>::Subscription>
       style_sheet_subscription_;
+#if !defined(OS_ANDROID)
   std::unique_ptr<ChromeZoomLevelPrefs::DefaultZoomLevelSubscription>
       default_zoom_level_subscription_;
+#endif  // !defined(OS_ANDROID)
   base::WeakPtrFactory<PrefsTabHelper> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefsTabHelper);
 };
 
 #endif  // CHROME_BROWSER_UI_PREFS_PREFS_TAB_HELPER_H_