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

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 5c8e89a199953dc1ae14d743f48f8a476135b5e7..00855a8933391c7fdda8b01423098cfa49e89e02 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -1626,6 +1626,9 @@ void HCheckInstanceType::GetCheckInterval(InstanceType* first,
     case IS_JS_ARRAY:
       *first = *last = JS_ARRAY_TYPE;
       return;
+    case IS_JS_DATE:
+      *first = *last = JS_DATE_TYPE;
+      return;
     default:
       UNREACHABLE();
   }
@@ -1695,6 +1698,8 @@ const char* HCheckInstanceType::GetCheckName() const {
   switch (check_) {
     case IS_SPEC_OBJECT: return "object";
     case IS_JS_ARRAY: return "array";
+    case IS_JS_DATE:
+      return "date";
     case IS_STRING: return "string";
     case IS_INTERNALIZED_STRING: return "internalized_string";
   }