Fix crashes: ComparisonInstr now has also kinds kIS and kISNOT: implement negation for those.

runtime/vm/token.h

 // Copyright (c) 2012, 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_TOKEN_H_
 #define VM_TOKEN_H_
 
 #include "platform/assert.h"
 
 namespace dart {
@@ skipping 286 matching lines @@
   static Token::Kind NegateComparison(Token::Kind op) {
     switch (op) {
       case Token::kEQ: return Token::kNE;
       case Token::kNE: return Token::kEQ;
       case Token::kLT: return Token::kGTE;
       case Token::kGT: return Token::kLTE;
       case Token::kLTE: return Token::kGT;
       case Token::kGTE: return Token::kLT;
       case Token::kEQ_STRICT: return Token::kNE_STRICT;
       case Token::kNE_STRICT: return Token::kEQ_STRICT;
+      case Token::kIS:    return Token::kISNOT;
+      case Token::kISNOT: return Token::kIS;
       default:
         UNREACHABLE();
         return Token::kILLEGAL;
     }
   }
 
  private:
   static const char* name_[];
   static const char* tok_str_[];
   static const uint8_t precedence_[];
   static const Attribute attributes_[];
 };
 
 
 }  // namespace dart
 
 #endif  // VM_TOKEN_H_