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

chrome/browser/ui/prefs/prefs_tab_helper.h

Index: chrome/browser/ui/prefs/prefs_tab_helper.h
diff --git a/chrome/browser/ui/prefs/prefs_tab_helper.h b/chrome/browser/ui/prefs/prefs_tab_helper.h
index 5a7079621b791f1daee3e4a61958d55fe17a4c13..9fd3acb138bc459d7ac58f87f0330bc15a3709b7 100644
--- a/chrome/browser/ui/prefs/prefs_tab_helper.h
+++ b/chrome/browser/ui/prefs/prefs_tab_helper.h
@@ -9,11 +9,14 @@
 #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 {
@@ -60,8 +63,10 @@ class PrefsTabHelper : public content::NotificationObserver,
   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);