Use kIllegalObjectKind instead of NULL object to terminate ICData array

runtime/vm/raw_object.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_RAW_OBJECT_H_
 #define VM_RAW_OBJECT_H_
 
 #include "platform/assert.h"
 #include "vm/globals.h"
 #include "vm/token.h"
@@ skipping 865 matching lines @@
   }
 };
 
 
 class RawICData : public RawObject {
   RAW_HEAP_OBJECT_IMPLEMENTATION(ICData);
 
   RawObject** from() {
     return reinterpret_cast<RawObject**>(&ptr()->function_);
   }
-  RawFunction* function_;  // Parent/calling function of this IC.
-  RawString* target_name_;  // Name of target function.
-  RawArray* ic_data_;  // Contains test class-ids and target functions.
+  RawFunction* function_;     // Parent/calling function of this IC.
+  RawString* target_name_;    // Name of target function.
+  RawArray* ic_data_;         // Contains test class-ids and target functions.
   RawObject** to() {
     return reinterpret_cast<RawObject**>(&ptr()->ic_data_);
   }
-  intptr_t id_;  // Parser node id corresponding to this IC.
+  intptr_t id_;               // Parser node id corresponding to this IC.
   intptr_t num_args_tested_;  // Number of arguments tested in IC.
 };
 
 
 class RawSubtypeTestCache : public RawObject {
   RAW_HEAP_OBJECT_IMPLEMENTATION(SubtypeTestCache);
   RawArray* cache_;
 };
 
 
@@ skipping 613 matching lines @@
          kExternalUint64Array == kByteArray + 18 &&
          kExternalFloat32Array == kByteArray + 19 &&
          kExternalFloat64Array == kByteArray + 20 &&
          kClosure == kByteArray + 21);
   return (index >= kByteArray && index <= kClosure);
 }
 
 }  // namespace dart
 
 #endif  // VM_RAW_OBJECT_H_