[vm, gc] Require a safepoint for heap iteration.

runtime/vm/isolate.h

 // 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.
 
 #ifndef RUNTIME_VM_ISOLATE_H_
 #define RUNTIME_VM_ISOLATE_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/atomic.h"
@@ skipping 160 matching lines @@
   static inline Isolate* Current() {
     Thread* thread = Thread::Current();
     return thread == NULL ? NULL : thread->isolate();
   }
 
   // Register a newly introduced class.
   void RegisterClass(const Class& cls);
   void RegisterClassAt(intptr_t index, const Class& cls);
   void ValidateClassTable();
 
-  // Visit all object pointers.
-  void IterateObjectPointers(ObjectPointerVisitor* visitor,
-                             bool validate_frames);
-  void IterateStackPointers(ObjectPointerVisitor* visitor,
-                            bool validate_frames);
-
   // Visits weak object pointers.
   void VisitWeakPersistentHandles(HandleVisitor* visitor);
 
   // Prepares all threads in an isolate for Garbage Collection.
   void PrepareForGC();
 
   StoreBuffer* store_buffer() { return store_buffer_; }
 
   ThreadRegistry* thread_registry() const { return thread_registry_; }
   SafepointHandler* safepoint_handler() const { return safepoint_handler_; }
@@ skipping 725 matching lines @@
   static bool creation_enabled_;
 
 #define REUSABLE_FRIEND_DECLARATION(name)                                      \
   friend class Reusable##name##HandleScope;
   REUSABLE_HANDLE_LIST(REUSABLE_FRIEND_DECLARATION)
 #undef REUSABLE_FRIEND_DECLARATION
 
   friend class Become;    // VisitObjectPointers
   friend class GCMarker;  // VisitObjectPointers
   friend class SafepointHandler;
+  friend class ObjectGraph;  // VisitObjectPointers
   friend class Scavenger;    // VisitObjectPointers
-  friend class ObjectGraph;  // VisitObjectPointers
+  friend class HeapIterationScope;  // VisitObjectPointers
   friend class ServiceIsolate;
   friend class Thread;
   friend class Timeline;
   friend class NoReloadScope;  // reload_block
 
   DISALLOW_COPY_AND_ASSIGN(Isolate);
 };
 
 // When we need to execute code in an isolate, we use the
 // StartIsolateScope.
@@ skipping 116 matching lines @@
   intptr_t* spawn_count_;
 
   Dart_IsolateFlags isolate_flags_;
   bool paused_;
   bool errors_are_fatal_;
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_ISOLATE_H_