[Isolates] Merge 6700:7030 from bleeding_edge to isolates.

src/array.js

Index: src/array.js
===================================================================
--- src/array.js	(revision 7031)
+++ src/array.js	(working copy)
@@ -161,15 +161,7 @@
     var result = %_FastAsciiArrayJoin(elements, separator);
     if (!IS_UNDEFINED(result)) return result;   
 
-    var length2 = (length << 1) - 1;
-    var j = length2;
-    var i = length;
-    elements[--j] = elements[--i];
-    while (i > 0) {
-      elements[--j] = separator;
-      elements[--j] = elements[--i];
-    }
-    return %StringBuilderConcat(elements, length2, '');    
+    return %StringBuilderJoin(elements, length, separator);
   } finally {
     // Make sure to remove the last element of the visited array no
     // matter what happens.
@@ -426,7 +418,6 @@
 
 
 function ArrayConcat(arg1) {  // length == 1
-  // TODO: can we just use arguments?
   var arg_count = %_ArgumentsLength();
   var arrays = new $Array(1 + arg_count);
   arrays[0] = this;
@@ -1026,13 +1017,13 @@
   }
   var min = index;
   var max = length;
-  if (UseSparseVariant(this, length, true)) {
+  if (UseSparseVariant(this, length, IS_ARRAY(this))) {
     var intervals = %GetArrayKeys(this, length);
     if (intervals.length == 2 && intervals[0] < 0) {
       // A single interval.
       var intervalMin = -(intervals[0] + 1);
       var intervalMax = intervalMin + intervals[1];
-      min = MAX(min, intervalMin);
+      if (min < intervalMin) min = intervalMin;
       max = intervalMax;  // Capped by length already.
       // Fall through to loop below.
     } else {
@@ -1082,13 +1073,13 @@
   }
   var min = 0;
   var max = index;
-  if (UseSparseVariant(this, length, true)) {
+  if (UseSparseVariant(this, length, IS_ARRAY(this))) {
     var intervals = %GetArrayKeys(this, index + 1);
     if (intervals.length == 2 && intervals[0] < 0) {
       // A single interval.
       var intervalMin = -(intervals[0] + 1);
       var intervalMax = intervalMin + intervals[1];
-      min = MAX(min, intervalMin);
+      if (min < intervalMin) min = intervalMin;
       max = intervalMax;  // Capped by index already.
       // Fall through to loop below.
     } else {