Optimize call sites that only ever have a single elements transition

src/ic.cc

Index: src/ic.cc
===================================================================
--- src/ic.cc	(revision 11733)
+++ src/ic.cc	(working copy)
@@ -1567,6 +1567,7 @@
   }
 
   bool monomorphic = false;
+  bool maybe_monomorphic = false;
   MapHandleList target_receiver_maps;
   if (ic_state != UNINITIALIZED && ic_state != PREMONOMORPHIC) {
     GetReceiverMapsForStub(Handle<Code>(target()), &target_receiver_maps);
@@ -1588,6 +1589,10 @@
             receiver->GetElementsKind());
       }
     }
+  } else {
+    if (ic_state == UNINITIALIZED || ic_state == PREMONOMORPHIC) {
+      maybe_monomorphic = true;
+    }
   }
 
   if (monomorphic) {
@@ -1600,6 +1605,7 @@
   // adding the map that was just encountered.
   Handle<Map> receiver_map(receiver->map());
   bool map_added =
+      maybe_monomorphic ? false :
       AddOneReceiverMapIfMissing(&target_receiver_maps, receiver_map);
   if (IsTransitionStubKind(stub_kind)) {
     Handle<Map> new_map = ComputeTransitionedMap(receiver, stub_kind);