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

base/values.cc

Index: base/values.cc
diff --git a/base/values.cc b/base/values.cc
index 8d7ca351d1e9cc6db28489f822a9f341906f04b5..ee84fc6c0ef90e3217b845f4e703fff9265418d7 100644
--- a/base/values.cc
+++ b/base/values.cc
@@ -694,6 +694,10 @@ void DictionaryValue::MergeDictionary(const DictionaryValue* dictionary) {
   }
 }
 
+void DictionaryValue::Swap(DictionaryValue* other) {
+  dictionary_.swap(other->dictionary_);
+}
+
 DictionaryValue* DictionaryValue::DeepCopy() const {
   DictionaryValue* result = new DictionaryValue;
 
@@ -908,6 +912,10 @@ ListValue::const_iterator ListValue::Find(const Value& value) const {
   return std::find_if(list_.begin(), list_.end(), ValueEquals(&value));
 }
 
+void ListValue::Swap(ListValue* other) {
+  list_.swap(other->list_);
+}
+
 bool ListValue::GetAsList(ListValue** out_value) {
   if (out_value)
     *out_value = this;