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diff --git a/vendor/go.opencensus.io/stats/measure.go b/vendor/go.opencensus.io/stats/measure.go
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+++ b/vendor/go.opencensus.io/stats/measure.go
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+// Copyright 2017, OpenCensus 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 stats
+
+import (
+        "sync"
+        "sync/atomic"
+)
+
+// Measure represents a single numeric value to be tracked and recorded.
+// For example, latency, request bytes, and response bytes could be measures
+// to collect from a server.
+//
+// Measures by themselves have no outside effects. In order to be exported,
+// the measure needs to be used in a View. If no Views are defined over a
+// measure, there is very little cost in recording it.
+type Measure interface {
+        // Name returns the name of this measure.
+        //
+        // Measure names are globally unique (among all libraries linked into your program).
+        // We recommend prefixing the measure name with a domain name relevant to your
+        // project or application.
+        //
+        // Measure names are never sent over the wire or exported to backends.
+        // They are only used to create Views.
+        Name() string
+
+        // Description returns the human-readable description of this measure.
+        Description() string
+
+        // Unit returns the units for the values this measure takes on.
+        //
+        // Units are encoded according to the case-sensitive abbreviations from the
+        // Unified Code for Units of Measure: http://unitsofmeasure.org/ucum.html
+        Unit() string
+}
+
+// measureDescriptor is the untyped descriptor associated with each measure.
+// Int64Measure and Float64Measure wrap measureDescriptor to provide typed
+// recording APIs.
+// Two Measures with the same name will have the same measureDescriptor.
+type measureDescriptor struct {
+        subs int32 // access atomically
+
+        name        string
+        description string
+        unit        string
+}
+
+func (m *measureDescriptor) subscribe() {
+        atomic.StoreInt32(&m.subs, 1)
+}
+
+func (m *measureDescriptor) subscribed() bool {
+        return atomic.LoadInt32(&m.subs) == 1
+}
+
+// Name returns the name of the measure.
+func (m *measureDescriptor) Name() string {
+        return m.name
+}
+
+// Description returns the description of the measure.
+func (m *measureDescriptor) Description() string {
+        return m.description
+}
+
+// Unit returns the unit of the measure.
+func (m *measureDescriptor) Unit() string {
+        return m.unit
+}
+
+var (
+        mu       sync.RWMutex
+        measures = make(map[string]*measureDescriptor)
+)
+
+func registerMeasureHandle(name, desc, unit string) *measureDescriptor {
+        mu.Lock()
+        defer mu.Unlock()
+
+        if stored, ok := measures[name]; ok {
+                return stored
+        }
+        m := &measureDescriptor{
+                name:        name,
+                description: desc,
+                unit:        unit,
+        }
+        measures[name] = m
+        return m
+}
+
+// Measurement is the numeric value measured when recording stats. Each measure
+// provides methods to create measurements of their kind. For example, Int64Measure
+// provides M to convert an int64 into a measurement.
+type Measurement struct {
+        v float64
+        m *measureDescriptor
+}
+
+// Value returns the value of the Measurement as a float64.
+func (m Measurement) Value() float64 {
+        return m.v
+}
+
+// Measure returns the Measure from which this Measurement was created.
+func (m Measurement) Measure() Measure {
+        return m.m
+}