metricsd: Fix upload service to compile with new libchrome version

libmetric's HistogramSnapshotManager::PrepareDeltas now takes the
iterators for the histogram collection to work on, instead of getting
a global one.

Change-Id: I3997ea7d2c330431379d055b0cb876069bddf395
diff --git a/uploader/upload_service.cc b/uploader/upload_service.cc
index 0dc59a4..333a7e6 100644
--- a/uploader/upload_service.cc
+++ b/uploader/upload_service.cc
@@ -183,6 +183,7 @@
   base::StatisticsRecorder::GetHistograms(&histograms);
 
   histogram_snapshot_manager_.PrepareDeltas(
+      histograms.begin(), histograms.end(),
       base::Histogram::kNoFlags, base::Histogram::kUmaTargetedHistogramFlag);
 
   // Gather and reset the crash counters, shared with the binder threads.