Homogenizes map checks for all polymorphic named field loads.

Tests show no perf regressions

BUG=

Review URL: https://codereview.chromium.org/14224009

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14259 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen.cc

@@ -6566,8 +6566,9 @@ bool HOptimizedGraphBuilder::HandlePolymorphicArrayLengthLoad(
   }
 
   AddInstruction(new(zone()) HCheckNonSmi(object));
+
   HInstruction* typecheck =
-    AddInstruction(HCheckInstanceType::NewIsJSArray(object, zone()));
+    AddInstruction(new(zone()) HCheckMaps(object, types, zone()));
   HInstruction* instr =
     HLoadNamedField::NewArrayLength(zone(), object, typecheck);
   instr->set_position(expr->position());