Use kIllegalObjectKind instead of NULL object to terminate ICData array

runtime/vm/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_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 2631 matching lines @@
         (index * sizeof(RawContextScope::VariableDesc));
     return reinterpret_cast<RawContextScope::VariableDesc*>(raw_addr);
   }
 
   HEAP_OBJECT_IMPLEMENTATION(ContextScope, Object);
   friend class Class;
 };
 
 
 // Object holding information about an IC: test classes and their
-// corresponding classes.
+// corresponding targets.
 class ICData : public Object {
  public:
   RawFunction* function() const {
     return raw_ptr()->function_;
   }
 
   RawString* target_name() const {
     return raw_ptr()->target_name_;
   }
 
@@ skipping 21 matching lines @@
 
   static intptr_t ic_data_offset() {
     return OFFSET_OF(RawICData, ic_data_);
   }
 
   static intptr_t function_offset() {
     return OFFSET_OF(RawICData, function_);
   }
 
   // Adds one more class test to ICData. Length of 'classes' must be equal to
-  // the number of arguments tested. Use only for number_of_checks > 1.
+  // the number of arguments tested. Use only for num_args_tested > 1.
   void AddCheck(const GrowableArray<intptr_t>& class_ids,
                 const Function& target) const;
   // Adds sorted so that Smi is the first class-id. Use only for
-  // number_of_checks == 1.
+  // num_args_tested == 1.
   void AddReceiverCheck(intptr_t receiver_class_id,
                         const Function& target) const;
   void GetCheckAt(intptr_t index,
                   GrowableArray<intptr_t>* class_ids,
                   Function* target) const;
   void GetOneClassCheckAt(
       int index, intptr_t* class_id, Function* target) const;
 
   intptr_t GetReceiverClassIdAt(intptr_t index) const;
   RawFunction* GetTargetAt(intptr_t index) const;
@@ skipping 13 matching lines @@
     return raw_ptr()->ic_data_;
   }
 
   void set_function(const Function& value) const;
   void set_target_name(const String& value) const;
   void set_id(intptr_t value) const;
   void set_num_args_tested(intptr_t value) const;
   void set_ic_data(const Array& value) const;
 
   intptr_t TestEntryLength() const;
+  void WriteSentinel() const;
 
   HEAP_OBJECT_IMPLEMENTATION(ICData, Object);
   friend class Class;
 };
 
 
 class SubtypeTestCache : public Object {
  public:
   enum Entries {
     kInstanceClassId = 0,
@@ skipping 2468 matching lines @@
     if (this->CharAt(i) != str.CharAt(begin_index + i)) {
       return false;
     }
   }
   return true;
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_