Make fewer assumptions about the layout of api handles.

runtime/vm/scavenger.cc

 // Copyright (c) 2011, 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/scavenger.h"
 
 #include <map>
 #include <utility>
 
 #include "vm/dart.h"
@@ skipping 177 matching lines @@
 
 
 class ScavengerWeakVisitor : public HandleVisitor {
  public:
   explicit ScavengerWeakVisitor(Scavenger* scavenger) : scavenger_(scavenger) {
   }
 
   void VisitHandle(uword addr) {
     FinalizablePersistentHandle* handle =
         reinterpret_cast<FinalizablePersistentHandle*>(addr);
-    RawObject** p = reinterpret_cast<RawObject**>(handle);
+    RawObject** p = handle->raw_addr();
     if (scavenger_->IsUnreachable(p)) {
       FinalizablePersistentHandle::Finalize(handle);
     }
   }
 
  private:
   Scavenger* scavenger_;
 
   DISALLOW_COPY_AND_ASSIGN(ScavengerWeakVisitor);
 };
@@ skipping 374 matching lines @@
   scavenging_ = false;
 }
 
 
 void Scavenger::WriteProtect(bool read_only) {
   space_->Protect(
       read_only ? VirtualMemory::kReadOnly : VirtualMemory::kReadWrite);
 }
 
 }  // namespace dart