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

chrome/browser/prefs/pref_model_associator.cc

Index: chrome/browser/prefs/pref_model_associator.cc
diff --git a/chrome/browser/prefs/pref_model_associator.cc b/chrome/browser/prefs/pref_model_associator.cc
index b70302a825f0e87aa57f4a4ec31bbe639ae8cbc1..abb419bb46a0ffdb0f86816bb7ca71f4e61c0f9c 100644
--- a/chrome/browser/prefs/pref_model_associator.cc
+++ b/chrome/browser/prefs/pref_model_associator.cc
@@ -48,8 +48,7 @@ void PrefModelAssociator::InitPrefAndAssociate(
         sync_pref.GetSpecifics().preference();
     DCHECK_EQ(pref->name(), preference.name());
 
-    scoped_ptr<Value> value(
-        reader.JsonToValue(preference.value(), false, false));
+    scoped_ptr<Value> value(reader.ReadToValue(preference.value()));
     if (!value.get()) {
       LOG(ERROR) << "Failed to deserialize preference value: "
                  << reader.GetErrorMessage();
@@ -350,7 +349,7 @@ Value* PrefModelAssociator::ReadPreferenceSpecifics(
     const sync_pb::PreferenceSpecifics& preference,
     std::string* name) {
   base::JSONReader reader;
-  scoped_ptr<Value> value(reader.JsonToValue(preference.value(), false, false));
+  scoped_ptr<Value> value(reader.ReadToValue(preference.value()));
   if (!value.get()) {
     std::string err = "Failed to deserialize preference value: " +
         reader.GetErrorMessage();