Handle LoadClassId(obj) === cid during type propagation.

runtime/vm/intermediate_language.h

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 7584 matching lines @@
   intptr_t ComputeCidMask() const;
   static bool IsDenseMask(intptr_t mask);
 
   virtual bool AllowsCSE() const { return true; }
   virtual EffectSet Dependencies() const;
   virtual EffectSet Effects() const { return EffectSet::None(); }
   virtual bool AttributesEqual(Instruction* other) const;
 
   void set_licm_hoisted(bool value) { licm_hoisted_ = value; }
 
+  static bool IsImmutableClassId(intptr_t cid);
+
  private:
   const ICData& unary_checks_;
   GrowableArray<intptr_t> cids_;  // Sorted, lowest first.
   bool licm_hoisted_;
   const intptr_t token_pos_;
 
   DISALLOW_COPY_AND_ASSIGN(CheckClassInstr);
 };
 
 
@@ skipping 421 matching lines @@
       Isolate* isolate, bool opt) const {                                     \
     UNIMPLEMENTED();                                                          \
     return NULL;                                                              \
   }                                                                           \
   void Name::EmitNativeCode(FlowGraphCompiler* compiler) { UNIMPLEMENTED(); }
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_