Allows turning on checked mode on a per-isolate basis

runtime/vm/isolate.cc

 // 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.
 
 #include "vm/isolate.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/json.h"
 #include "vm/code_observers.h"
@@ skipping 437 matching lines @@
       object_store_(NULL),
       top_exit_frame_info_(0),
       init_callback_data_(NULL),
       environment_callback_(NULL),
       library_tag_handler_(NULL),
       api_state_(NULL),
       stub_code_(NULL),
       debugger_(NULL),
       single_step_(false),
       resume_request_(false),
+      checked_mode_(false),
       random_(),
       simulator_(NULL),
       long_jump_base_(NULL),
       timer_list_(),
       deopt_id_(0),
       mutex_(new Mutex()),
       stack_limit_(0),
       saved_stack_limit_(0),
       stack_base_(0),
       stack_overflow_flags_(0),
@@ skipping 1178 matching lines @@
                            serialized_message_, serialized_message_len_);
 }
 
 
 void IsolateSpawnState::Cleanup() {
   SwitchIsolateScope switch_scope(I);
   Dart::ShutdownIsolate();
 }
 
 }  // namespace dart