Implement UMA log throttling for cellular connections

chrome/browser/io_thread.h

Index: chrome/browser/io_thread.h
diff --git a/chrome/browser/io_thread.h b/chrome/browser/io_thread.h
index d21ce618c06973ebb2744fb3c549e972bc4ee315..82bc5509c5b65f1d75a089e03abb44f6d8782287 100644
--- a/chrome/browser/io_thread.h
+++ b/chrome/browser/io_thread.h
@@ -24,6 +24,7 @@
 #include "build/build_config.h"
 #include "chrome/browser/net/chrome_network_delegate.h"
 #include "chrome/common/features.h"
+#include "components/metrics/data_use_tracker.h"
 #include "components/prefs/pref_member.h"
 #include "components/ssl_config/ssl_config_service_manager.h"
 #include "content/public/browser/browser_thread.h"
@@ -599,6 +600,8 @@ class IOThread : public content::BrowserThreadDelegate {
 
   const base::TimeTicks creation_time_;
 
+  base::WeakPtr<metrics::DataUseTracker> data_use_tracker_;
+
   base::WeakPtrFactory<IOThread> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(IOThread);