oauth2: avoid using http.DefaultTransport

transport_test.go

Index: transport_test.go 
diff --git a/transport_test.go b/transport_test.go 
index 847266a37a6988b056282583b0f554de85c91102..e5bfe6f8582dfd461b11b8dadeb605bc45007332 100644 
--- a/transport_test.go 
+++ b/transport_test.go 
@@ -14,7 +14,7 @@ func (f *mockTokenFetcher) FetchToken(existing *Token) (*Token, error) { 
 } 
 
 func TestInitialTokenRead(t *testing.T) { 
-	tr := NewAuthorizedTransport(nil, &Token{AccessToken: "abc"}) 
+	tr := NewAuthorizedTransport(http.DefaultTransport, nil, &Token{AccessToken: "abc"}) 
	server := newMockServer(func(w http.ResponseWriter, r *http.Request) { 
	if r.Header.Get("Authorization") != "Bearer abc" { 
	t.Errorf("Transport doesn't set the Authorization header from the initial token") 
@@ -31,7 +31,7 @@ func TestTokenFetch(t *testing.T) { 
	AccessToken: "abc", 
	}, 
	} 
-	tr := NewAuthorizedTransport(fetcher, nil) 
+	tr := NewAuthorizedTransport(http.DefaultTransport, fetcher, nil) 
	server := newMockServer(func(w http.ResponseWriter, r *http.Request) { 
	if r.Header.Get("Authorization") != "Bearer abc" { 
	t.Errorf("Transport doesn't set the Authorization header from the fetched token")