Decouple Metrics Initialization from IO Thread Initialization

chrome/browser/profiles/profile_impl_io_data.h

Index: chrome/browser/profiles/profile_impl_io_data.h
diff --git a/chrome/browser/profiles/profile_impl_io_data.h b/chrome/browser/profiles/profile_impl_io_data.h
index 0058267e40a4509bc5d1d628b168422c82fe027e..f64fbc88380c9c07ced83c348f74e7f312a63bb7 100644
--- a/chrome/browser/profiles/profile_impl_io_data.h
+++ b/chrome/browser/profiles/profile_impl_io_data.h
@@ -234,6 +234,10 @@ class ProfileImplIOData : public ProfileIOData {
   int app_cache_max_size_;
   int app_media_cache_max_size_;
 
+  // Callback for updating data use prefs which needs to be initialized on UI
+  // thread and passed to the network delegate.
+  const metrics::UpdateUsagePrefCallbackType metrics_data_use_forwarder_;
+
   DISALLOW_COPY_AND_ASSIGN(ProfileImplIOData);
 };