Object size on heap map hover.

runtime/vm/isolate.h

Index: runtime/vm/isolate.h
===================================================================
--- runtime/vm/isolate.h	(revision 35314)
+++ runtime/vm/isolate.h	(working copy)
@@ -10,6 +10,7 @@
 #include "platform/thread.h"
 #include "vm/base_isolate.h"
 #include "vm/class_table.h"
+#include "vm/counters.h"
 #include "vm/handles.h"
 #include "vm/megamorphic_cache_table.h"
 #include "vm/random.h"
@@ -492,6 +493,8 @@
   void set_current_tag(const UserTag& tag);
   void clear_current_tag();
 
+  Counters* counters() { return &counters_; }
+
 #if defined(DEBUG)
 #define REUSABLE_HANDLE_SCOPE_ACCESSORS(object)                                \
   void set_reusable_##object##_handle_scope_active(bool value) {               \
@@ -584,6 +587,8 @@
   RawGrowableObjectArray* tag_table_;
   RawUserTag* current_tag_;
 
+  Counters counters_;
+
   // Isolate list next pointer.
   Isolate* next_;