Add runtime function for string to array conversion.

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index 6310eac6b3e93c526dc337ba341c3e79faf8bd97..aba9e4161ccbd26fd382e75350f485ba829dec31 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -2967,6 +2967,18 @@ Object* Heap::AllocateFixedArray(int length, PretenureFlag pretenure) {
 }
 
 
+Object* Heap::AllocateUninitializedFixedArray(int length) {
+  if (length == 0) return empty_fixed_array();
+
+  Object* obj = AllocateRawFixedArray(length);
+  if (obj->IsFailure()) return obj;
+
+  reinterpret_cast<FixedArray*>(obj)->set_map(fixed_array_map());
+  FixedArray::cast(obj)->set_length(length);
+  return obj;
+}
+
+
 Object* Heap::AllocateFixedArrayWithHoles(int length) {
   if (length == 0) return empty_fixed_array();
   Object* result = AllocateRawFixedArray(length);