- Create isolate specific resuable handles and use them in the hot lookup paths.

runtime/vm/base_isolate.h

 // 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.
 
 #ifndef VM_BASE_ISOLATE_H_
 #define VM_BASE_ISOLATE_H_
 
 namespace dart {
 
 class HandleScope;
@@ skipping 77 matching lines @@
     ASSERT(no_callback_scope_depth_ < INT_MAX);
     no_callback_scope_depth_ += 1;
   }
 
   void DecrementNoCallbackScopeDepth() {
     ASSERT(no_callback_scope_depth_ > 0);
     no_callback_scope_depth_ -= 1;
   }
 
 #if defined(DEBUG)
+  void set_reusable_handle_scope_active(bool value) {
+    reusable_handle_scope_active_ = value;
+  }
+
+  bool reusable_handle_scope_active() {
+    return reusable_handle_scope_active_;
+  }
+#endif
+
+#if defined(DEBUG)
   static void AssertCurrent(BaseIsolate* isolate);
 #endif
 
  protected:
   BaseIsolate()
       : top_resource_(NULL),
         current_zone_(NULL),
 #if defined(DEBUG)
         top_handle_scope_(NULL),
         no_handle_scope_depth_(0),
         no_gc_scope_depth_(0),
+        reusable_handle_scope_active_(false),
 #endif
         no_callback_scope_depth_(0)
   {}
 
   ~BaseIsolate() {
     // Do not delete stack resources: top_resource_ and current_zone_.
   }
 
   StackResource* top_resource_;
   Zone* current_zone_;
 #if defined(DEBUG)
   HandleScope* top_handle_scope_;
   int32_t no_handle_scope_depth_;
   int32_t no_gc_scope_depth_;
+  bool reusable_handle_scope_active_;
 #endif
   int32_t no_callback_scope_depth_;
 
+ private:
   DISALLOW_COPY_AND_ASSIGN(BaseIsolate);
 };
 
 }  // namespace dart
 
 #endif  // VM_BASE_ISOLATE_H_