Tune Array.forEach, fix Array functions

src/js/array.js

Index: src/js/array.js
diff --git a/src/js/array.js b/src/js/array.js
index a42aad590cd8a1905a29a16148544093a2e6d6ea..58e7f59e79811ef5929ec238a26d93255577c024 100644
--- a/src/js/array.js
+++ b/src/js/array.js
@@ -1257,10 +1257,19 @@ function InnerArrayForEach(f, receiver, array, length) {
   if (!IS_CALLABLE(f)) throw MakeTypeError(kCalledNonCallable, f);
 
   var is_array = IS_ARRAY(array);
-  for (var i = 0; i < length; i++) {
-    if (HAS_INDEX(array, i, is_array)) {
-      var element = array[i];
-      %_Call(f, receiver, element, i, array);
+  if (IS_UNDEFINED(receiver)) {

[adamk, 2016/02/18 17:43:32]

FWIW we used to do something even fancier, but bmeurer removed it in
https://codereview.chromium.org/1325573004/diff/60001/src/array.js (partly
because it wasn't entirely correct).

[Toon Verwaest, 2016/02/24 09:09:03]

That code was quite different. The bug there iirc comes from the TO_OBJECT
that's both invalidly cached and created in the wrong context.

+    for (var i = 0; i < length; i++) {
+      if (HAS_INDEX(array, i, is_array)) {
+        var element = array[i];
+        f(element, i, array);
+      }
+    }
+  } else {
+    for (var i = 0; i < length; i++) {
+      if (HAS_INDEX(array, i, is_array)) {
+        var element = array[i];
+        %_Call(f, receiver, element, i, array);
+      }
     }
   }
 }