Convert JsonWriter::Write to taking a const ref for the in-param

chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager_policy_browsertest.cc

 // Copyright 2014 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 <string>
 #include <vector>
 
 #include "ash/desktop_background/desktop_background_controller.h"
 #include "ash/desktop_background/desktop_background_controller_observer.h"
 #include "ash/shell.h"
@@ skipping 202 matching lines @@
     }
   }
 
   std::string ConstructPolicy(const std::string& relative_path) const {
     std::string image_data;
     if (!base::ReadFileToString(test_data_dir_.Append(relative_path),
                                 &image_data)) {
       ADD_FAILURE();
     }
     std::string policy;
-    base::JSONWriter::Write(policy::test::ConstructExternalDataReference(
-        embedded_test_server()->GetURL(std::string("/") + relative_path).spec(),
-        image_data).get(),
-        &policy);
+    base::JSONWriter::Write(*policy::test::ConstructExternalDataReference(
+                                embedded_test_server()
+                                    ->GetURL(std::string("/") + relative_path)
+                                    .spec(),
+                                image_data),
+                            &policy);
     return policy;
   }
 
   // Inject |filename| as wallpaper policy for test user |user_number|.  Set
   // empty |filename| to clear policy.
   void InjectPolicy(int user_number, const std::string& filename) {
     ASSERT_TRUE(user_number == 0 || user_number == 1);
     const std::string user_id = kTestUsers[user_number];
     policy::UserPolicyBuilder* builder =
         user_policy_builders_[user_number].get();
@@ skipping 159 matching lines @@
 
 IN_PROC_BROWSER_TEST_F(WallpaperManagerPolicyTest, PersistOverLogout) {
   LoginUser(kTestUsers[0]);
 
   // Wait until wallpaper has been loaded.
   RunUntilWallpaperChangeCount(1);
   ASSERT_EQ(kRedImageColor, GetAverageBackgroundColor());
 }
 
 }  // namespace chromeos