Fix a couple of isolate-related memory leaks that show up a lot in valgrind output.

runtime/vm/isolate.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/isolate.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/bigint_store.h"
 #include "vm/code_index_table.h"
@@ skipping 63 matching lines @@
 Isolate::~Isolate() {
   delete [] name_;
   delete message_queue_;
   delete heap_;
   delete object_store_;
   // Do not delete stack resources: top_resource_ and current_zone_.
   delete bigint_store_;
   delete api_state_;
   delete stub_code_;
   delete code_index_table_;
+  delete debugger_;
   delete mutex_;
   mutex_ = NULL;  // Fail fast if interrupts are scheduled on a dead isolate.
 }
 
 
 static bool StandardPostMessageCallback(Dart_Isolate dart_isolate,
                                         Dart_Port dest_port,
                                         Dart_Port reply_port,
                                         Dart_Message dart_message) {
   Isolate* isolate = reinterpret_cast<Isolate*>(dart_isolate);
@@ skipping 300 matching lines @@
 }
 
 
 void Isolate::VisitWeakPersistentHandles(HandleVisitor* visitor) {
   if (api_state() != NULL) {
     api_state()->VisitWeakHandles(visitor);
   }
 }
 
 }  // namespace dart