vendor: update all dependencies to latest versions

vendor/cloud.google.com/go/trace/apiv1/doc.go

@@ -1,4 +1,4 @@
-// Copyright 2017, Google Inc. All rights reserved.
+// Copyright 2017, Google LLC All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -14,13 +14,16 @@
 
 // AUTO-GENERATED CODE. DO NOT EDIT.
 
-// Package trace is an experimental, auto-generated package for the
+// Package trace is an auto-generated package for the
 // Stackdriver Trace API.
 //
-// Send and retrieve trace data from Stackdriver Trace. Data is generated and
-// available by default for all App Engine applications. Data from other
-// applications can be written to Stackdriver Trace for display, reporting,
-// and analysis.
+//   NOTE: This package is in alpha. It is not stable, and is likely to change.
+//
+// Sends application trace data to Stackdriver Trace for viewing. Trace data
+// is
+// collected for all App Engine applications by default. Trace data from
+// other
+// applications can be provided using this API.
 //
 // Use the client at cloud.google.com/go/trace in preference to this.
 package trace // import "cloud.google.com/go/trace/apiv1"
@@ -30,11 +33,15 @@ import (
 	"google.golang.org/grpc/metadata"
 )
 
-func insertXGoog(ctx context.Context, val []string) context.Context {
-	md, _ := metadata.FromOutgoingContext(ctx)
-	md = md.Copy()
-	md["x-goog-api-client"] = val
-	return metadata.NewOutgoingContext(ctx, md)
+func insertMetadata(ctx context.Context, mds ...metadata.MD) context.Context {
+	out, _ := metadata.FromOutgoingContext(ctx)
+	out = out.Copy()
+	for _, md := range mds {
+		for k, v := range md {
+			out[k] = append(out[k], v...)
+		}
+	}
+	return metadata.NewOutgoingContext(ctx, out)
 }
 
 // DefaultAuthScopes reports the default set of authentication scopes to use with this package.