Added unit annotation supports onto tsmon in go.

common/tsmon/types/cell.go

Index: common/tsmon/types/cell.go
diff --git a/common/tsmon/types/cell.go b/common/tsmon/types/cell.go
index 410757d72f7090feeebafb41f14a0ecced99f94c..7712103f150237f910dc67c58fdd048b9080fc2f 100644
--- a/common/tsmon/types/cell.go
+++ b/common/tsmon/types/cell.go
@@ -16,6 +16,7 @@ import (
 // type.
 type Cell struct {
 	MetricInfo
+	MetricMetadata
 	CellData
 }
 
@@ -27,6 +28,11 @@ type MetricInfo struct {
 	ValueType   ValueType
 }
 
+// MetricMetadata contains user-provided metadata for a metric.
+type MetricMetadata struct {
+	Units MetricDataUnits // the unit of recorded data for a given metric.
+}
+
 // CellData contains the value of a single cell.
 type CellData struct {
 	FieldVals []interface{}