Don't use SmartSlice just because the receiver is an array.

Only do so if the estimated number of elements is low compared to the
end position for the slice. This is similar to other heuristics used
for array operations that use the %GetElementKeys runtime function.

R=erik.corry@gmail.com

Review URL: http://codereview.chromium.org/7111032

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8184 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/array.js

@@ -631,7 +631,9 @@ function ArraySlice(start, end) {
 
   if (end_i < start_i) return result;
 
-  if (IS_ARRAY(this)) {
+  if (IS_ARRAY(this) &&
+      (end_i > 1000) &&
+      (%EstimateNumberOfElements(this) < end_i)) {
     SmartSlice(this, start_i, end_i - start_i, len, result);
   } else {
     SimpleSlice(this, start_i, end_i - start_i, len, result);