Use timer task runner for V8PerIsolate tasks

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 <stddef.h>
 #include <stdint.h>
 
 #include <string>
 #include <utility>
 
 #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"
 #include "base/strings/utf_string_conversions.h"
+#include "base/threading/thread_task_runner_handle.h"
 #include "gin/array_buffer.h"
 #include "gin/public/isolate_holder.h"
 #include "gin/v8_initializer.h"
 #include "mojo/common/data_pipe_utils.h"
 #include "mojo/edk/js/mojo_runner_delegate.h"
 #include "mojo/edk/js/tests/js_to_cpp.mojom.h"
 #include "mojo/edk/test/test_utils.h"
 #include "mojo/public/cpp/bindings/binding.h"
 #include "mojo/public/cpp/bindings/lib/validation_errors.h"
 #include "mojo/public/cpp/system/core.h"
@@ skipping 369 matching lines @@
     js_side->SetCppSide(std::move(cpp_side_ptr));
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
     gin::V8Initializer::LoadV8Snapshot();
     gin::V8Initializer::LoadV8Natives();
 #endif
 
     gin::IsolateHolder::Initialize(gin::IsolateHolder::kStrictMode,
                                    gin::IsolateHolder::kStableV8Extras,
                                    gin::ArrayBufferAllocator::SharedInstance());
-    gin::IsolateHolder instance;
+    gin::IsolateHolder instance(base::ThreadTaskRunnerHandle::Get());
     MojoRunnerDelegate delegate;
     gin::ShellRunner runner(&delegate, instance.isolate());
     delegate.Start(&runner, js_side_proxy.PassMessagePipe().release().value(),
                    test);
 
     run_loop_.Run();
   }
 
  private:
   base::ShadowingAtExitManager at_exit_;
@@ skipping 29 matching lines @@
   mojo::internal::ScopedSuppressValidationErrorLoggingForTests log_suppression;
 
   BackPointerCppSideConnection cpp_side_connection;
   RunTest("mojo/edk/js/tests/js_to_cpp_tests", &cpp_side_connection);
   EXPECT_TRUE(cpp_side_connection.DidSucceed());
 }
 
 }  // namespace js
 }  // namespace edk
 }  // namespace mojo