Revert "Hide Isolate pointer from embedder"

runtime/vm/debugger_api_impl.cc

Index: runtime/vm/debugger_api_impl.cc
diff --git a/runtime/vm/debugger_api_impl.cc b/runtime/vm/debugger_api_impl.cc
index ae802a7a6347cd2d5088803ae84d2f3934a2a8d2..5b1c8680b33e26d9c7ccdea871af7e3b8794a7c5 100644
--- a/runtime/vm/debugger_api_impl.cc
+++ b/runtime/vm/debugger_api_impl.cc
@@ -976,16 +976,14 @@ DART_EXPORT Dart_Handle Dart_SetLibraryDebuggable(intptr_t library_id,
 
 
 DART_EXPORT Dart_Isolate Dart_GetIsolate(Dart_IsolateId isolate_id) {
-  // Dart_Isolate is now the same as Dart_IsolateId.
-  // TODO(johnmccutchan): Kill Dart_IsolateId.
-  return static_cast<Dart_Isolate>(isolate_id);
+  Isolate* isolate = PortMap::GetIsolate(isolate_id);
+  return Api::CastIsolate(isolate);
 }
 
 
 DART_EXPORT Dart_IsolateId Dart_GetIsolateId(Dart_Isolate dart_isolate) {
-  // Dart_Isolate is now the same as Dart_IsolateId.
-  // TODO(johnmccutchan): Kill Dart_IsolateId.
-  return static_cast<Dart_IsolateId>(dart_isolate);
+  Isolate* isolate = reinterpret_cast<Isolate*>(dart_isolate);
+  return isolate->debugger()->GetIsolateId();
 }
 
 }  // namespace dart