Avoid one repeated property lookup when computing load ICs.

src/field-index.h

Index: src/field-index.h
diff --git a/src/field-index.h b/src/field-index.h
index 096b33509f7d40dd16d7f046df897b70d511fdf5..6aa4be761a18cfc40d7d4287a97675af1ff920bb 100644
--- a/src/field-index.h
+++ b/src/field-index.h
@@ -11,6 +11,7 @@
 namespace v8 {
 namespace internal {
 
+class LookupIterator;
 class Map;
 
 // Wrapper class to hold a field index, usually but not necessarily generated
@@ -24,6 +25,7 @@ class FieldIndex V8_FINAL {
                                      bool is_double = false);
   static FieldIndex ForInObjectOffset(int offset, Map* map = NULL);
   static FieldIndex ForLookupResult(const LookupResult* result);
+  static FieldIndex ForLookupIterator(const LookupIterator* lookup);
   static FieldIndex ForDescriptor(Map* map, int descriptor_index);
   static FieldIndex ForLoadByFieldIndex(Map* map, int index);
   static FieldIndex ForKeyedLookupCacheIndex(Map* map, int index);