chore(storage): fix progress call in gRPC Writer

Fixes googleapis#7798

storage/grpc_client.go

@@ -1060,11 +1060,13 @@ func (c *grpcStorageClient) OpenWriter(params *openWriterParams, opts ...storage
 				pr.CloseWithError(err)
 				return
 			}
-			// At this point, the current buffer has been uploaded. Capture the
-			// committed offset here in case the upload was not finalized and
-			// another chunk is to be uploaded.
-			offset = off
-			progress(offset)
+			// At this point, the current buffer has been uploaded. For resumable
+			// uploads, capture the committed offset here in case the upload was not
+			// finalized and another chunk is to be uploaded.
+			if gw.upid != "" {
+				offset = off
+				progress(offset)
+			}
 
 			// When we are done reading data and the chunk has been finalized,
 			// we are done.

storage/integration_test.go

@@ -2251,7 +2251,7 @@ func TestIntegration_WriterContentType(t *testing.T) {
 }
 
 func TestIntegration_WriterChunksize(t *testing.T) {
-	ctx := skipJSONReads(skipGRPC("https://github.com/googleapis/google-cloud-go/issues/7839"), "no reads in test")
+	ctx := skipJSONReads(context.Background(), "no reads in test")
 	multiTransportTest(ctx, t, func(t *testing.T, ctx context.Context, bucket, _ string, client *Client) {
 		obj := client.Bucket(bucket).Object("writer-chunksize-test" + uidSpaceObjects.New())
 		objSize := 1<<10<<10 + 1 // 1 Mib + 1 byte