Metrics explicitly implement Metric interface

prometheus/counter.go

@@ -14,14 +14,13 @@ import (
 // TODO(matt): Refactor to de-duplicate behaviors.
 
 type Counter interface {
-	AsMarshallable() map[string]interface{}
+	Metric
+
 	Decrement(labels map[string]string) float64
 	DecrementBy(labels map[string]string, value float64) float64
 	Increment(labels map[string]string) float64
 	IncrementBy(labels map[string]string, value float64) float64
-	ResetAll()
 	Set(labels map[string]string, value float64) float64
-	String() string
 }
 
 type counterVector struct {

prometheus/gauge.go

@@ -16,10 +16,8 @@ import (
 // temperature or the hitherto bandwidth used, this would be the metric for such
 // circumstances.
 type Gauge interface {
-	AsMarshallable() map[string]interface{}
-	ResetAll()
+	Metric
 	Set(labels map[string]string, value float64) float64
-	String() string
 }
 
 type gaugeVector struct {

prometheus/histogram.go

@@ -52,10 +52,8 @@ type HistogramSpecification struct {
 }
 
 type Histogram interface {
+	Metric
 	Add(labels map[string]string, value float64)
-	AsMarshallable() map[string]interface{}
-	ResetAll()
-	String() string
 }
 
 // The histogram is an accumulator for samples.  It merely routes into which