Set V8 extras mode in gin::V8Initializer.

mojo/edk/js/tests/js_to_cpp_tests.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/at_exit.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
@@ skipping 363 matching lines @@
     js_to_cpp::JsSidePtr js_side;
     auto js_side_proxy = GetProxy(&js_side);
 
     cpp_side->set_js_side(js_side.get());
     js_to_cpp::CppSidePtr cpp_side_ptr;
     cpp_side->Bind(GetProxy(&cpp_side_ptr));
 
     js_side->SetCppSide(cpp_side_ptr.Pass());
 
     gin::IsolateHolder::Initialize(gin::IsolateHolder::kStrictMode,
+                                   gin::IsolateHolder::kStableV8Extras,
                                    gin::ArrayBufferAllocator::SharedInstance());
     gin::IsolateHolder instance;
     MojoRunnerDelegate delegate;
     gin::ShellRunner runner(&delegate, instance.isolate());
     delegate.Start(&runner, js_side_proxy.PassMessagePipe().release().value(),
                    test);
 
     run_loop_.Run();
   }
 
@@ skipping 24 matching lines @@
 }
 
 TEST_F(JsToCppTest, BackPointer) {
   BackPointerCppSideConnection cpp_side_connection;
   RunTest("mojo/edk/js/tests/js_to_cpp_tests", &cpp_side_connection);
   EXPECT_TRUE(cpp_side_connection.DidSucceed());
 }
 
 }  // namespace edk
 }  // namespace mojo