Fix LoadFieldByIndex to take mutable heap-numbers into account.

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index 696c6be6e8159cd8ba3427dab2f8eb6e0717400c..aa8fe3a2611541a9e641ee828751d423c5c151bd 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -2702,7 +2702,9 @@ LInstruction* LChunkBuilder::DoCheckMapValue(HCheckMapValue* instr) {
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
-  return DefineSameAsFirst(new(zone()) LLoadFieldByIndex(object, index));
+  LLoadFieldByIndex* load = new(zone()) LLoadFieldByIndex(object, index);
+  LInstruction* result = DefineSameAsFirst(load);
+  return AssignPointerMap(result);
 }