Use mutable heapnumbers to store doubles in fields.

src/ia32/lithium-ia32.h

Index: src/ia32/lithium-ia32.h
diff --git a/src/ia32/lithium-ia32.h b/src/ia32/lithium-ia32.h
index 062744ad9440cd9eb6462800d47be969777353b7..704ffa22fe57af31ba6638f3843550f2ca5c67c9 100644
--- a/src/ia32/lithium-ia32.h
+++ b/src/ia32/lithium-ia32.h
@@ -1489,15 +1489,13 @@ class LReturn: public LTemplateInstruction<0, 3, 0> {
 };
 
 
-class LLoadNamedField: public LTemplateInstruction<1, 1, 1> {
+class LLoadNamedField: public LTemplateInstruction<1, 1, 0> {
  public:
-  explicit LLoadNamedField(LOperand* object, LOperand* temp) {
+  explicit LLoadNamedField(LOperand* object) {
     inputs_[0] = object;
-    temps_[0] = temp;
   }
 
   LOperand* object() { return inputs_[0]; }
-  LOperand* temp() { return temps_[0]; }
 
   DECLARE_CONCRETE_INSTRUCTION(LoadNamedField, "load-named-field")
   DECLARE_HYDROGEN_ACCESSOR(LoadNamedField)