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

chrome/common/net/gaia/oauth2_mint_token_flow.cc

Index: chrome/common/net/gaia/oauth2_mint_token_flow.cc
diff --git a/chrome/common/net/gaia/oauth2_mint_token_flow.cc b/chrome/common/net/gaia/oauth2_mint_token_flow.cc
index c39bbaa74d5dcb536c84a470f67ad98ee59c4b6a..ca5391f9b45947d3d171109dd2c306335f12d6dd 100644
--- a/chrome/common/net/gaia/oauth2_mint_token_flow.cc
+++ b/chrome/common/net/gaia/oauth2_mint_token_flow.cc
@@ -184,8 +184,7 @@ void OAuth2MintTokenFlow::ProcessApiCallSuccess(
   // internal error.
   std::string response_body;
   source->GetResponseAsString(&response_body);
-  base::JSONReader reader;
-  scoped_ptr<base::Value> value(reader.Read(response_body, false));
+  scoped_ptr<base::Value> value(base::JSONReader::Read(response_body));
   DictionaryValue* dict = NULL;
   if (!value.get() || !value->GetAsDictionary(&dict)) {
     ReportFailure(GoogleServiceAuthError::FromConnectionError(101));