Move preferred scrollbar style preference change listening from renderer to browser, 2 of 3.

content/browser/browser_main_loop.cc

Index: content/browser/browser_main_loop.cc
diff --git a/content/browser/browser_main_loop.cc b/content/browser/browser_main_loop.cc
index 250cb369360774ebeffb6aae20d5769907cb2d8a..246f8232b8f417be7727a63f2d869adebd4378a1 100644
--- a/content/browser/browser_main_loop.cc
+++ b/content/browser/browser_main_loop.cc
@@ -72,7 +72,7 @@
 #include "content/browser/android/surface_texture_peer_browser_impl.h"
 #endif
 
-#if defined(OS_MACOSX)
+#if defined(OS_MACOSX) && !defined(OS_IOS)
 #include "content/browser/theme_helper_mac.h"
 #endif
 
@@ -1029,11 +1029,12 @@ int BrowserMainLoop::BrowserThreadsStarted() {
             GpuProcessHost::GPU_PROCESS_KIND_SANDBOXED,
             CAUSE_FOR_GPU_LAUNCH_BROWSER_STARTUP));
   }
-#endif  // !defined(OS_IOS)
 
 #if defined(OS_MACOSX)
   ThemeHelperMac::GetInstance();
 #endif
+#endif  // !defined(OS_IOS)
+
   return result_code_;
 }