Make UMA stats creation available in the Java interface.

webrtc/system_wrappers/source/metrics_default.cc

Index: webrtc/system_wrappers/source/metrics_default.cc
diff --git a/webrtc/system_wrappers/source/metrics_default.cc b/webrtc/system_wrappers/source/metrics_default.cc
index 49004543ea177938a7cd49a6ab6a784f5af26ee8..fd7610b1130bdd5956ceb8516ee7fb510206fd7d 100644
--- a/webrtc/system_wrappers/source/metrics_default.cc
+++ b/webrtc/system_wrappers/source/metrics_default.cc
@@ -244,6 +244,15 @@ void HistogramAdd(Histogram* histogram_pointer,
   ptr->Add(sample);
 }
 
+// Fast path. Adds |sample| to cached |histogram_pointer|.
+void HistogramAdd(Histogram* histogram_pointer, int sample) {
+  if (!histogram_pointer)
+    return;
+
+  RtcHistogram* ptr = reinterpret_cast<RtcHistogram*>(histogram_pointer);
+  ptr->Add(sample);
+}
+
 SampleInfo::SampleInfo(const std::string& name,
                        int min,
                        int max,