Don't fast RemoveArrayHoles in case of arguments arrays.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 140c3234e6bed870ad706b7a96ff8d5e99ed7d77..61ebc0ad55122767412e82aac5d6367e8986dc14 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -10508,11 +10508,17 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_GlobalPrint) {
 // and are followed by non-existing element. Does not change the length
 // property.
 // Returns the number of non-undefined elements collected.
+// Returns -1 if hole removal is not supported by this method.
 RUNTIME_FUNCTION(MaybeObject*, Runtime_RemoveArrayHoles) {
   HandleScope scope(isolate);
   ASSERT(args.length() == 2);
   CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
   CONVERT_NUMBER_CHECKED(uint32_t, limit, Uint32, args[1]);
+  if (object->HasFastArgumentsElements() ||

[Michael Starzinger, 2014/03/12 13:31:57]

nit: Instead of putting this logic here, can we move it into
JSObject::PrepareElementsForSort instead?

+      object->HasDictionaryArgumentsElements() ||

[Michael Starzinger, 2014/03/12 13:31:57]

nit: Better use object->HasNonStrictArgumentsElements() instead of asking for
"fast" and "dictionary" separately.

+      object->map()->is_observed()) {
+    return Smi::FromInt(-1);
+  }
   return *JSObject::PrepareElementsForSort(object, limit);
 }