diff --git a/vendor/google.golang.org/grpc/attributes/attributes.go b/vendor/google.golang.org/grpc/attributes/attributes.go
index 3220d87..6ff2792 100644
--- a/vendor/google.golang.org/grpc/attributes/attributes.go
+++ b/vendor/google.golang.org/grpc/attributes/attributes.go
@@ -25,55 +25,75 @@
 // later release.
 package attributes
 
-import "fmt"
-
 // Attributes is an immutable struct for storing and retrieving generic
 // key/value pairs.  Keys must be hashable, and users should define their own
-// types for keys.
+// types for keys.  Values should not be modified after they are added to an
+// Attributes or if they were received from one.  If values implement 'Equal(o
+// interface{}) bool', it will be called by (*Attributes).Equal to determine
+// whether two values with the same key should be considered equal.
 type Attributes struct {
 	m map[interface{}]interface{}
 }
 
-// New returns a new Attributes containing all key/value pairs in kvs.  If the
-// same key appears multiple times, the last value overwrites all previous
-// values for that key.  Panics if len(kvs) is not even.
-func New(kvs ...interface{}) *Attributes {
-	if len(kvs)%2 != 0 {
-		panic(fmt.Sprintf("attributes.New called with unexpected input: len(kvs) = %v", len(kvs)))
-	}
-	a := &Attributes{m: make(map[interface{}]interface{}, len(kvs)/2)}
-	for i := 0; i < len(kvs)/2; i++ {
-		a.m[kvs[i*2]] = kvs[i*2+1]
-	}
-	return a
+// New returns a new Attributes containing the key/value pair.
+func New(key, value interface{}) *Attributes {
+	return &Attributes{m: map[interface{}]interface{}{key: value}}
 }
 
-// WithValues returns a new Attributes containing all key/value pairs in a and
-// kvs.  Panics if len(kvs) is not even.  If the same key appears multiple
-// times, the last value overwrites all previous values for that key.  To
-// remove an existing key, use a nil value.
-func (a *Attributes) WithValues(kvs ...interface{}) *Attributes {
+// WithValue returns a new Attributes containing the previous keys and values
+// and the new key/value pair.  If the same key appears multiple times, the
+// last value overwrites all previous values for that key.  To remove an
+// existing key, use a nil value.  value should not be modified later.
+func (a *Attributes) WithValue(key, value interface{}) *Attributes {
 	if a == nil {
-		return New(kvs...)
+		return New(key, value)
 	}
-	if len(kvs)%2 != 0 {
-		panic(fmt.Sprintf("attributes.New called with unexpected input: len(kvs) = %v", len(kvs)))
-	}
-	n := &Attributes{m: make(map[interface{}]interface{}, len(a.m)+len(kvs)/2)}
+	n := &Attributes{m: make(map[interface{}]interface{}, len(a.m)+1)}
 	for k, v := range a.m {
 		n.m[k] = v
 	}
-	for i := 0; i < len(kvs)/2; i++ {
-		n.m[kvs[i*2]] = kvs[i*2+1]
-	}
+	n.m[key] = value
 	return n
 }
 
 // Value returns the value associated with these attributes for key, or nil if
-// no value is associated with key.
+// no value is associated with key.  The returned value should not be modified.
 func (a *Attributes) Value(key interface{}) interface{} {
 	if a == nil {
 		return nil
 	}
 	return a.m[key]
 }
+
+// Equal returns whether a and o are equivalent.  If 'Equal(o interface{})
+// bool' is implemented for a value in the attributes, it is called to
+// determine if the value matches the one stored in the other attributes.  If
+// Equal is not implemented, standard equality is used to determine if the two
+// values are equal.
+func (a *Attributes) Equal(o *Attributes) bool {
+	if a == nil && o == nil {
+		return true
+	}
+	if a == nil || o == nil {
+		return false
+	}
+	if len(a.m) != len(o.m) {
+		return false
+	}
+	for k, v := range a.m {
+		ov, ok := o.m[k]
+		if !ok {
+			// o missing element of a
+			return false
+		}
+		if eq, ok := v.(interface{ Equal(o interface{}) bool }); ok {
+			if !eq.Equal(ov) {
+				return false
+			}
+		} else if v != ov {
+			// Fallback to a standard equality check if Value is unimplemented.
+			return false
+		}
+	}
+	return true
+}