Faster moving FixedArray elements around.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 2ad698c0af3200bd24fda22bf6d1687b6dfe32f1..a33930ef6c497ab2a3d150cf2389b5a75bd49389 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -1397,6 +1397,11 @@ void FixedArray::set_the_hole(int index) {
 }
 
 
+Object** FixedArray::data_start() {
+  return HeapObject::RawField(this, kHeaderSize);
+}
+
+
 bool DescriptorArray::IsEmpty() {
   ASSERT(this == Heap::empty_descriptor_array() ||
          this->length() > 2);