[date] Refactor the %_DateField intrinsic to be optimizable.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 5916860f766ba0f2adac6145d801db1a5d0848af..f99fa35b0f0714e79dd42a02c654305ad1578d37 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -11928,6 +11928,17 @@ void HOptimizedGraphBuilder::GenerateJSValueGetValue(CallRuntime* call) {
 }
 
 
+void HOptimizedGraphBuilder::GenerateThrowIfNotADate(CallRuntime* call) {
+  DCHECK_EQ(1, call->arguments()->length());
+  CHECK_ALIVE(VisitForValue(call->arguments()->at(0)));
+  HValue* obj = Pop();
+  BuildCheckHeapObject(obj);
+  HCheckInstanceType* check =
+      New<HCheckInstanceType>(obj, HCheckInstanceType::IS_JS_DATE);
+  return ast_context()->ReturnInstruction(check, call->id());
+}
+
+
 void HOptimizedGraphBuilder::GenerateDateField(CallRuntime* call) {
   DCHECK(call->arguments()->length() == 2);
   DCHECK_NOT_NULL(call->arguments()->at(1)->AsLiteral());