Measuring data use of different ModelTypes in Sync Service.

sync/engine/process_updates_util.cc

Index: sync/engine/process_updates_util.cc
diff --git a/sync/engine/process_updates_util.cc b/sync/engine/process_updates_util.cc
index 9b428ef929bd9c8ba80705e028dd91f8ce2a39bb..46c27bfdf735fc5a585b1135cb6b3821b20e6c2a 100644
--- a/sync/engine/process_updates_util.cc
+++ b/sync/engine/process_updates_util.cc
@@ -15,6 +15,7 @@
 #include "sync/syncable/syncable_proto_util.h"
 #include "sync/syncable/syncable_util.h"
 #include "sync/util/cryptographer.h"
+#include "sync/util/data_type_histogram.h"
 
 namespace syncer {
 
@@ -303,6 +304,13 @@ void ProcessDownloadedUpdates(
     if (verify_result != VERIFY_SUCCESS && verify_result != VERIFY_UNDELETE)
       continue;
     ProcessUpdate(**update_it, dir->GetCryptographer(trans), trans);
+    if ((*update_it)->ByteSize() > 0) {
+      UMA_HISTOGRAM_SPARSE_SLOWLY_WITH_VALUE("DataUse.Sync.Download.Bytes",
+                                             ModelTypeToHistogramInt(type),
+                                             (*update_it)->ByteSize());
+    }
+    UMA_HISTOGRAM_SPARSE_SLOWLY("DataUse.Sync.Download.Count",
+                                ModelTypeToHistogramInt(type));
   }
 }