LibJS: Ignore arguments in Date's constructor when called as a function

Since theres no way to drop the arguments before the call to the
constructor (or to signal to the constructor that it was not called
directly), we simply reuse the code for the no arguments provided
special case. (And to prevent code duplication, the code was extracted
into the separate static function Date::now(GlobalObject&).

Userland/Libraries/LibJS/Runtime/Date.cpp

@@ -9,6 +9,8 @@
 #include <LibJS/Heap/Heap.h>
 #include <LibJS/Runtime/Date.h>
 #include <LibJS/Runtime/GlobalObject.h>
+#include <sys/time.h>
+#include <time.h>
 
 namespace JS {
 
@@ -17,6 +19,15 @@ Date* Date::create(GlobalObject& global_object, Core::DateTime datetime, u16 mil
     return global_object.heap().allocate<Date>(global_object, datetime, milliseconds, is_invalid, *global_object.date_prototype());
 }
 
+Date* Date::now(GlobalObject& global_object)
+{
+    struct timeval tv;
+    gettimeofday(&tv, nullptr);
+    auto datetime = Core::DateTime::now();
+    auto milliseconds = static_cast<u16>(tv.tv_usec / 1000);
+    return create(global_object, datetime, milliseconds);
+}
+
 Date::Date(Core::DateTime datetime, u16 milliseconds, bool is_invalid, Object& prototype)
     : Object(prototype)
     , m_datetime(datetime)