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

base/values.h

Index: base/values.h
diff --git a/base/values.h b/base/values.h
index 4bcdc7526e44b39352fdf1763e2ad4c04860a125..1d35d63934f8e93abba97295532c1fa54780b348 100644
--- a/base/values.h
+++ b/base/values.h
@@ -303,11 +303,12 @@ class BASE_EXPORT DictionaryValue : public Value {
   // passed out via out_value.  If |out_value| is NULL, the removed value will
   // be deleted.  This method returns true if |path| is a valid path; otherwise
   // it will return false and the DictionaryValue object will be unchanged.
-  bool Remove(const std::string& path, Value** out_value);
+  virtual bool Remove(const std::string& path, Value** out_value);
 
   // Like Remove(), but without special treatment of '.'.  This allows e.g. URLs
   // to be used as paths.
-  bool RemoveWithoutPathExpansion(const std::string& key, Value** out_value);
+  virtual bool RemoveWithoutPathExpansion(const std::string& key,
+                                          Value** out_value);
 
   // Makes a copy of |this| but doesn't include empty dictionaries and lists in
   // the copy.  This never returns NULL, even if |this| itself is empty.
@@ -321,9 +322,7 @@ class BASE_EXPORT DictionaryValue : public Value {
   void MergeDictionary(const DictionaryValue* dictionary);
 
   // Swaps contents with the |other| dictionary.
-  void Swap(DictionaryValue* other) {
-    dictionary_.swap(other->dictionary_);
-  }
+  virtual void Swap(DictionaryValue* other);
 
   // This class provides an iterator for the keys in the dictionary.
   // It can't be used to modify the dictionary.
@@ -425,7 +424,7 @@ class BASE_EXPORT ListValue : public Value {
   // passed out via |out_value|.  If |out_value| is NULL, the removed value will
   // be deleted.  This method returns true if |index| is valid; otherwise
   // it will return false and the ListValue object will be unchanged.
-  bool Remove(size_t index, Value** out_value);
+  virtual bool Remove(size_t index, Value** out_value);
 
   // Removes the first instance of |value| found in the list, if any, and
   // deletes it. |index| is the location where |value| was found. Returns false
@@ -450,9 +449,7 @@ class BASE_EXPORT ListValue : public Value {
   const_iterator Find(const Value& value) const;
 
   // Swaps contents with the |other| list.
-  void Swap(ListValue* other) {
-    list_.swap(other->list_);
-  }
+  virtual void Swap(ListValue* other);
 
   // Iteration.
   iterator begin() { return list_.begin(); }