Address Florian's comments.

runtime/vm/object.cc

 // 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.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
@@ skipping 7383 matching lines @@
 
 void ICData::WriteSentinel() const {
   const Smi& sentinel_value = Smi::Handle(Smi::New(kIllegalCid));
   const Array& data = Array::Handle(ic_data());
   for (intptr_t i = 1; i <= TestEntryLength(); i++) {
     data.SetAt(data.Length() - i, sentinel_value);
   }
 }
 
 
+#if defined(DEBUG)
 // Used in asserts to verify that a check is not added twice.
 bool ICData::HasCheck(const GrowableArray<intptr_t>& cids) const {
   for (intptr_t i = 0; i < NumberOfChecks(); i++) {
     GrowableArray<intptr_t> class_ids;
     Function& target = Function::Handle();
     GetCheckAt(i, &class_ids, &target);
     bool matches = true;
     for (intptr_t k = 0; k < class_ids.length(); k++) {
       if (class_ids[k] != cids[k]) {
         matches = false;
         break;
       }
     }
     if (matches) {
       return true;
     }
   }
   return false;
 }
+#endif  // DEBUG
 
 
 void ICData::AddCheck(const GrowableArray<intptr_t>& class_ids,
                       const Function& target) const {
-  ASSERT(!HasCheck(class_ids));
+  DEBUG_ASSERT(!HasCheck(class_ids));
   ASSERT(num_args_tested() > 1);  // Otherwise use 'AddReceiverCheck'.
   ASSERT(class_ids.length() == num_args_tested());
   const intptr_t old_num = NumberOfChecks();
   Array& data = Array::Handle(ic_data());
   const intptr_t new_len = data.Length() + TestEntryLength();
   data = Array::Grow(data, new_len, Heap::kOld);
   set_ic_data(data);
   WriteSentinel();
   intptr_t data_pos = old_num * TestEntryLength();
   for (intptr_t i = 0; i < class_ids.length(); i++) {
@@ skipping 4758 matching lines @@
   }
   return result.raw();
 }
 
 
 const char* WeakProperty::ToCString() const {
   return "_WeakProperty";
 }
 
 }  // namespace dart