[runtime] Migrate several Date builtins to C++.

src/execution.h

Index: src/execution.h
diff --git a/src/execution.h b/src/execution.h
index afbd1da45b2c2854c42cbe724671a772e1441f21..9feda335a23fb77269397af86dfbcd596d62ac7a 100644
--- a/src/execution.h
+++ b/src/execution.h
@@ -13,9 +13,6 @@
 namespace v8 {
 namespace internal {
 
-// Forward declarations.
-class JSRegExp;
-
 class Execution final : public AllStatic {
  public:
   // Call a function, the caller supplies a receiver and an array
@@ -56,10 +53,6 @@ class Execution final : public AllStatic {
   MUST_USE_RESULT static MaybeHandle<Object> ToObject(
       Isolate* isolate, Handle<Object> obj);
 
-  // Create a new date object from 'time'.
-  MUST_USE_RESULT static MaybeHandle<Object> NewDate(
-      Isolate* isolate, double time);
-
   static Handle<String> GetStackTraceLine(Handle<Object> recv,
                                           Handle<JSFunction> fun,
                                           Handle<Object> pos,