Remove isolate parameter when allocating handles

runtime/vm/dart_api_impl.h

Index: runtime/vm/dart_api_impl.h
diff --git a/runtime/vm/dart_api_impl.h b/runtime/vm/dart_api_impl.h
index 2f635d3097092a3cb4be4f681c8be1b27461759c..a1bb236070374a7eeaaba7309df0c2a944ad3c86 100644
--- a/runtime/vm/dart_api_impl.h
+++ b/runtime/vm/dart_api_impl.h
@@ -75,10 +75,10 @@ const char* CanonicalFunction(const char* func);
   HANDLESCOPE(T);
 
 
-#define RETURN_TYPE_ERROR(isolate, dart_handle, type)                          \
+#define RETURN_TYPE_ERROR(zone, dart_handle, type)                             \
   do {                                                                         \
     const Object& tmp =                                                        \
-        Object::Handle(isolate, Api::UnwrapHandle((dart_handle)));             \
+        Object::Handle(zone, Api::UnwrapHandle((dart_handle)));                \
     if (tmp.IsNull()) {                                                        \
       return Api::NewError("%s expects argument '%s' to be non-null.",         \
                            CURRENT_FUNC, #dart_handle);                        \
@@ -132,7 +132,7 @@ class Api : AllStatic {
   // Unwraps a raw Type from the handle.  The handle will be null if
   // the object was not of the requested Type.
 #define DECLARE_UNWRAP(Type)                                                   \
-  static const Type& Unwrap##Type##Handle(Isolate* isolate,                    \
+  static const Type& Unwrap##Type##Handle(Zone* zone,                          \
                                           Dart_Handle object);
   CLASS_LIST_FOR_HANDLES(DECLARE_UNWRAP)
 #undef DECLARE_UNWRAP