Turn the NumberToStringStub into a hydrogen stub.

src/code-stubs-hydrogen.cc

Index: src/code-stubs-hydrogen.cc
diff --git a/src/code-stubs-hydrogen.cc b/src/code-stubs-hydrogen.cc
index 0d06209b613db0f9dc46d32dbab532591edd720d..af37c29cca2e8e88dac1162b1b392fef88fce7d7 100644
--- a/src/code-stubs-hydrogen.cc
+++ b/src/code-stubs-hydrogen.cc
@@ -339,6 +339,19 @@ Handle<Code> ToNumberStub::GenerateCode(Isolate* isolate) {
 
 
 template <>
+HValue* CodeStubGraphBuilder<NumberToStringStub>::BuildCodeStub() {
+  info()->MarkAsSavesCallerDoubles();
+  HValue* number = GetParameter(NumberToStringStub::kNumber);
+  return BuildNumberToString(number);
+}
+
+
+Handle<Code> NumberToStringStub::GenerateCode(Isolate* isolate) {
+  return DoGenerateCode(isolate, this);
+}
+
+
+template <>
 HValue* CodeStubGraphBuilder<FastCloneShallowArrayStub>::BuildCodeStub() {
   Factory* factory = isolate()->factory();
   HValue* undefined = graph()->GetConstantUndefined();