Rewrite base::JSONReader to be 35-40% faster, depending on the input string.

chrome/test/base/ui_test_utils.cc

 // Copyright (c) 2012 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 "chrome/test/base/ui_test_utils.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #endif
 
@@ skipping 223 matching lines @@
   std::string json;
   if (!dom_op_observer.GetResponse(&json)) {
     DLOG(ERROR) << "Cannot communicate with DOMOperationObserver.";
     return false;
   }
 
   // Nothing more to do for callers that ignore the returned JS value.
   if (!result)
     return true;
 
-  // Wrap |json| in an array before deserializing because valid JSON has an
-  // array or an object as the root.
-  json.insert(0, "[");
-  json.append("]");
-
-  scoped_ptr<Value> root_val(
-      base::JSONReader::Read(json, base::JSON_ALLOW_TRAILING_COMMAS));
-  if (!root_val->IsType(Value::TYPE_LIST)) {
-    DLOG(ERROR) << "JSON result is not a list.";
+  base::JSONReader reader(base::JSON_ALLOW_TRAILING_COMMAS);
+  result->reset(reader.ReadToValue(json));
+  if (!result->get()) {
+    DLOG(ERROR) << reader.GetErrorMessage();
     return false;
   }
 
-  ListValue* list = static_cast<ListValue*>(root_val.get());
-  Value* result_val;
-  if (!list || !list->GetSize() ||
-      // Remove gives us ownership of the value.
-      !list->Remove(0, &result_val)) {
-    DLOG(ERROR) << "JSON result list is empty.";
-    return false;
-  }
-
-  result->reset(result_val);
   return true;
 }
 
 void RunAllPendingMessageAndSendQuit(content::BrowserThread::ID thread_id) {
   MessageLoop::current()->PostTask(FROM_HERE, MessageLoop::QuitClosure());
   RunMessageLoop();
   content::BrowserThread::PostTask(thread_id, FROM_HERE,
                                    MessageLoop::QuitClosure());
 }
 
@@ skipping 905 matching lines @@
                int state,
                const base::Closure& followup) {
   if (!followup.is_null())
     ui_controls::SendMouseEventsNotifyWhenDone(button, state, followup);
   else
     ui_controls::SendMouseEvents(button, state);
 }
 
 }  // namespace internal
 }  // namespace ui_test_utils