Revert "Hide Isolate pointer from embedder"

runtime/vm/dart_api_impl.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_DART_API_IMPL_H_
 #define VM_DART_API_IMPL_H_
 
 #include "vm/allocation.h"
 #include "vm/native_arguments.h"
 #include "vm/object.h"
@@ skipping 131 matching lines @@
   static const Instance& UnwrapInstanceHandle(
       const ReusableObjectHandleScope& reused, Dart_Handle object);
 
   // Returns an Error handle if isolate is in an inconsistent state
   // or there was an error while finalizing classes.
   // Returns a Success handle when no error condition exists.
   static Dart_Handle CheckAndFinalizePendingClasses(Isolate *isolate);
 
   // Casts the internal Isolate* type to the external Dart_Isolate type.
   static Dart_Isolate CastIsolate(Isolate* isolate);
-  // Casts the external Dart_Isolate type to the internal Isolate* type.
-  static Isolate* CastIsolate(Dart_Isolate);
 
   // Gets the handle used to designate successful return.
   static Dart_Handle Success() { return Api::True(); }
 
   // Sets up the acquired error object after initializing an Isolate. This
   // object is pre-created because we will not be able to allocate this
   // object when the error actually occurs. When the error occurs there will
   // be outstanding acquires to internal data pointers making it unsafe to
   // allocate objects on the dart heap.
   static void SetupAcquiredError(Isolate* isolate);
@@ skipping 152 matching lines @@
   if (isolate->no_callback_scope_depth() != 0) {                               \
     return reinterpret_cast<Dart_Handle>(Api::AcquiredError(isolate));         \
   }                                                                            \
 
 #define ASSERT_CALLBACK_STATE(isolate)                                         \
   ASSERT(isolate->no_callback_scope_depth() == 0)
 
 }  // namespace dart.
 
 #endif  // VM_DART_API_IMPL_H_