Reuse the top ApiLocalScope so that we do not allocate and free an ApiLocalScope

runtime/vm/handles.h

 // 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.
 
 #ifndef VM_HANDLES_H_
 #define VM_HANDLES_H_
 
 #include "vm/allocation.h"
 #include "vm/flags.h"
 #include "vm/os.h"
@@ skipping 81 matching lines @@
   // Visit all blocks that have been added since the last time
   // this method was called.
   // Be careful with this, since multiple users of this method could
   // interfere with eachother.
   // Currently only used by GC trace facility.
   void VisitUnvisitedScopedHandles(ObjectPointerVisitor* visitor);
 
   // Visit all of the various handles.
   void Visit(HandleVisitor* visitor);
 
+  // Reset the handles so that we can reuse.
+  void Reset();
+
   // Allocates a handle in the current handle scope. This handle is valid only
   // in the current handle scope and is destroyed when the current handle
   // scope ends.
   static uword AllocateHandle(Isolate* isolate);
 
   // Allocates a handle in the current zone. This handle will be destroyed
   // when the current zone is destroyed.
   static uword AllocateZoneHandle(Isolate* isolate);
 
   // Returns true if specified handle is a zone handle.
@@ skipping 226 matching lines @@
 };
 #endif  // defined(DEBUG)
 
 // Macro to start a no handles scope in the code.
 #define NOHANDLESCOPE(isolate)                                                 \
     dart::NoHandleScope no_vm_internal_handles_scope_(isolate);
 
 }  // namespace dart
 
 #endif  // VM_HANDLES_H_