Update GCS storage library to support GetObject API on gzipped objects (#6506)

Fixes #6280

vendor/google.golang.org/api/option/credentials_notgo19.go

@@ -0,0 +1,32 @@
+// Copyright 2018 Google LLC
+//
+// 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.
+
+// +build !go1.9
+
+package option
+
+import (
+	"golang.org/x/oauth2/google"
+	"google.golang.org/api/internal"
+)
+
+type withCreds google.DefaultCredentials
+
+func (w *withCreds) Apply(o *internal.DialSettings) {
+	o.Credentials = (*google.DefaultCredentials)(w)
+}
+
+func WithCredentials(creds *google.DefaultCredentials) ClientOption {
+	return (*withCreds)(creds)
+}