Update tracing dependencies

vendor/github.com/uber/jaeger-lib/metrics/histogram.go

@@ -0,0 +1,28 @@
+// Copyright (c) 2018 The Jaeger Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package metrics
+
+// Histogram that keeps track of a distribution of values.
+type Histogram interface {
+	// Records the value passed in.
+	Record(float64)
+}
+
+// NullHistogram that does nothing
+var NullHistogram Histogram = nullHistogram{}
+
+type nullHistogram struct{}
+
+func (nullHistogram) Record(float64) {}