Assert no allocation during heap iteration; fix unsafe iteration in ObjectGraph.

runtime/vm/pages.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/pages.h"
 
 #include "platform/assert.h"
 #include "vm/compiler_stats.h"
 #include "vm/gc_marker.h"
 #include "vm/gc_sweeper.h"
@@ skipping 65 matching lines @@
 }
 
 
 void HeapPage::Deallocate() {
   // The memory for this object will become unavailable after the delete below.
   delete memory_;
 }
 
 
 void HeapPage::VisitObjects(ObjectVisitor* visitor) const {
+  NoSafepointScope no_safepoint;
   uword obj_addr = object_start();
   uword end_addr = object_end();
   while (obj_addr < end_addr) {
     RawObject* raw_obj = RawObject::FromAddr(obj_addr);
     visitor->VisitObject(raw_obj);
     obj_addr += raw_obj->Size();
   }
   ASSERT(obj_addr == end_addr);
 }
 
 
 void HeapPage::VisitObjectPointers(ObjectPointerVisitor* visitor) const {
+  NoSafepointScope no_safepoint;
   uword obj_addr = object_start();
   uword end_addr = object_end();
   while (obj_addr < end_addr) {
     RawObject* raw_obj = RawObject::FromAddr(obj_addr);
     obj_addr += raw_obj->VisitPointers(visitor);
   }
   ASSERT(obj_addr == end_addr);
 }
 
 
@@ skipping 1024 matching lines @@
     return 0;
   } else {
     ASSERT(total_time >= gc_time);
     int result = static_cast<int>((static_cast<double>(gc_time) /
                                    static_cast<double>(total_time)) * 100);
     return result;
   }
 }
 
 }  // namespace dart