Use timer task runner for V8PerIsolate tasks

gin/shell/gin_main.cc

Index: gin/shell/gin_main.cc
diff --git a/gin/shell/gin_main.cc b/gin/shell/gin_main.cc
index e73ce1f6dd0a02cbae2675eae0ffe0b555fc9a75..c7cf598756d8538415970900911efa9b264401d4 100644
--- a/gin/shell/gin_main.cc
+++ b/gin/shell/gin_main.cc
@@ -80,8 +80,7 @@ int main(int argc, char** argv) {
   gin::IsolateHolder::Initialize(gin::IsolateHolder::kStrictMode,
                                  gin::IsolateHolder::kStableV8Extras,
                                  gin::ArrayBufferAllocator::SharedInstance());
-  gin::IsolateHolder instance;
-
+  gin::IsolateHolder instance(base::ThreadTaskRunnerHandle::Get());
 
   gin::GinShellRunnerDelegate delegate;
   gin::ShellRunner runner(&delegate, instance.isolate());