Implement basic array prefetching hints in Hydrogen.

src/ia32/lithium-ia32.h

Index: src/ia32/lithium-ia32.h
===================================================================
--- src/ia32/lithium-ia32.h	(revision 13123)
+++ src/ia32/lithium-ia32.h	(working copy)
@@ -1407,15 +1407,20 @@
 };
 
 
-class LLoadKeyed: public LTemplateInstruction<1, 2, 0> {
+class LLoadKeyed: public LTemplateInstruction<1, 3, 1> {
  public:
-  LLoadKeyed(LOperand* elements, LOperand* key) {
+  LLoadKeyed(LOperand* elements, LOperand* key, LOperand* prefetch_distance,
+             LOperand* temp) {
     inputs_[0] = elements;
     inputs_[1] = key;
+    inputs_[2] = prefetch_distance;
+    temps_[0] = temp;
   }
 
   LOperand* elements() { return inputs_[0]; }
   LOperand* key() { return inputs_[1]; }
+  LOperand* prefetch_distance() { return inputs_[2]; }
+  LOperand* temp() { return temps_[0]; }
   ElementsKind elements_kind() const {
     return hydrogen()->elements_kind();
   }