[es6] Move builtin constructors for primitives to strict mode.

test/mjsunit/regress/regress-105.js

Index: test/mjsunit/regress/regress-105.js
diff --git a/test/mjsunit/regress/regress-105.js b/test/mjsunit/regress/regress-105.js
index 8b8030ffec0288e6812ae3785f672a6b3beb6e48..877cb82317a4514b2abc23c844be648fa95812af 100644
--- a/test/mjsunit/regress/regress-105.js
+++ b/test/mjsunit/regress/regress-105.js
@@ -26,12 +26,12 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 var custom_valueOf = function() {
-  assertEquals(Number, custom_valueOf.caller);
+  assertEquals(null, custom_valueOf.caller);
   return 2;
 }
 
 var custom_toString = function() {
-  assertEquals(String, custom_toString.caller);
+  assertEquals(null, custom_toString.caller);
   return "I used to be an adventurer like you";
 }