Make isolate id getter public.

src/isolate.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1089 matching lines @@
     return sweeper_thread_;
   }
 
   CallbackTable* callback_table() {
     return callback_table_;
   }
   void set_callback_table(CallbackTable* callback_table) {
     callback_table_ = callback_table;
   }
 
+  int id() const { return static_cast<int>(id_); }
+
   HStatistics* GetHStatistics();
   HTracer* GetHTracer();
 
  private:
   Isolate();
 
-  int id() const { return static_cast<int>(id_); }
-
   friend struct GlobalState;
   friend struct InitializeGlobalState;
 
   enum State {
     UNINITIALIZED,    // Some components may not have been allocated.
     INITIALIZED       // All components are fully initialized.
   };
 
   // These fields are accessed through the API, offsets must be kept in sync
   // with v8::internal::Internals (in include/v8.h) constants. This is also
@@ skipping 363 matching lines @@
 
 // Mark the native context with out of memory.
 inline void Context::mark_out_of_memory() {
   native_context()->set_out_of_memory(HEAP->true_value());
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_ISOLATE_H_