detect preferences errors

chrome/browser/extensions/image_loading_tracker_unittest.cc

 // Copyright (c) 2010 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 "base/message_loop.h"
 #include "base/path_service.h"
 #include "chrome/browser/chrome_thread.h"
 #include "chrome/browser/extensions/image_loading_tracker.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/json_value_serializer.h"
@@ skipping 38 matching lines @@
 
   Extension* CreateExtension() {
     // Create and load an extension.
     FilePath test_file;
     if (!PathService::Get(chrome::DIR_TEST_DATA, &test_file)) {
       EXPECT_FALSE(true);
       return NULL;
     }
     test_file = test_file.AppendASCII("extensions")
                          .AppendASCII("image_loading_tracker");
+    int error_code;
     std::string error;
     JSONFileValueSerializer serializer(test_file.AppendASCII("app.json"));
     scoped_ptr<DictionaryValue> valid_value(
-        static_cast<DictionaryValue*>(serializer.Deserialize(&error)));
-    EXPECT_EQ("", error);
-    if (error != "")
+        static_cast<DictionaryValue*>(serializer.Deserialize(&error_code,
+                                                             &error)));
+    EXPECT_EQ(0, error_code) << error;
+    if (error_code != 0)
       return NULL;
 
     EXPECT_TRUE(valid_value.get());
     if (!valid_value.get())
       return NULL;
 
     scoped_ptr<Extension> extension(new Extension(test_file));
     if (!extension->InitFromValue(*valid_value, false, &error))
       return NULL;
 
@@ skipping 91 matching lines @@
 
   WaitForImageLoad();
 
   // Even though we deleted the extension, we should still get the image.
   // We should still have gotten the image.
   EXPECT_EQ(1, image_loaded_count());
 
   // Check that the image was loaded.
   EXPECT_EQ(Extension::EXTENSION_ICON_SMALLISH, image_.width());
 }