Replace (most) occurrences of mojo::Array<T>() with nullptr.

mojo/public/cpp/bindings/tests/versioning_test_service.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <map>
 
 #include "mojo/public/c/system/main.h"
 #include "mojo/public/cpp/application/application_connection.h"
 #include "mojo/public/cpp/application/application_delegate.h"
 #include "mojo/public/cpp/application/application_runner.h"
@@ skipping 49 matching lines @@
     if (employees_.find(id) == employees_.end())
       employees_[id] = new EmployeeInfo();
     employees_[id]->employee = employee.Pass();
     callback.Run(true);
   }
 
   void QueryEmployee(uint64_t id,
                      bool retrieve_finger_print,
                      const QueryEmployeeCallback& callback) override {
     if (employees_.find(id) == employees_.end()) {
-      callback.Run(nullptr, Array<uint8_t>());
+      callback.Run(nullptr, nullptr);
       return;
     }
-    callback.Run(employees_[id]->employee.Clone(),
-                 retrieve_finger_print ? employees_[id]->finger_print.Clone()
-                                       : Array<uint8_t>());
+    callback.Run(
+        employees_[id]->employee.Clone(),
+        retrieve_finger_print ? employees_[id]->finger_print.Clone() : nullptr);
   }
 
   void AttachFingerPrint(uint64_t id,
                          Array<uint8_t> finger_print,
                          const AttachFingerPrintCallback& callback) override {
     if (employees_.find(id) == employees_.end()) {
       callback.Run(false);
       return;
     }
     employees_[id]->finger_print = finger_print.Pass();
@@ skipping 30 matching lines @@
 }  // namespace versioning
 }  // namespace test
 }  // namespace mojo
 
 MojoResult MojoMain(MojoHandle application_request) {
   mojo::ApplicationRunner runner(
       new mojo::test::versioning::HumanResourceSystemServer());
 
   return runner.Run(application_request);
 }