Implement UMA log throttling for cellular connections

chrome/browser/profiles/profile_io_data.h

Index: chrome/browser/profiles/profile_io_data.h
diff --git a/chrome/browser/profiles/profile_io_data.h b/chrome/browser/profiles/profile_io_data.h
index 15166f29307b0a3896d8c16fcbc5b141ef853ea8..917a3378d43fe6d210cca3e0226e07d733f48677 100644
--- a/chrome/browser/profiles/profile_io_data.h
+++ b/chrome/browser/profiles/profile_io_data.h
@@ -597,6 +597,10 @@ class ProfileIOData {
 
   const Profile::ProfileType profile_type_;
 
+  // Callback for updating data use prefs which needs to be initialized on UI
+  // thread and passed to |ChromeNetworkDelegate|.
+  metrics::UpdateUsagePrefCallbackType metrics_data_use_forwarder_;
+
   DISALLOW_COPY_AND_ASSIGN(ProfileIOData);
 };