1. Restructure reusable handles to make individual Scopes for each handle type

runtime/vm/base_isolate.h

Index: runtime/vm/base_isolate.h
===================================================================
--- runtime/vm/base_isolate.h	(revision 33332)
+++ runtime/vm/base_isolate.h	(working copy)
@@ -95,16 +95,6 @@
   }
 
 #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
 
@@ -116,7 +106,6 @@
         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)
   {}
@@ -131,7 +120,6 @@
   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_;