Make DispatchKeyEventPostIME() asynchronous.

services/ui/ime/ime_unittest.cc

Index: services/ui/ime/ime_unittest.cc
diff --git a/services/ui/ime/ime_unittest.cc b/services/ui/ime/ime_unittest.cc
index 8471c680096e4253924cd2ff0ee7af4875165c2d..b2f93286a3372e7e2aa6ee5cd2e8b364561b74a3 100644
--- a/services/ui/ime/ime_unittest.cc
+++ b/services/ui/ime/ime_unittest.cc
@@ -39,6 +39,11 @@ class TestTextInputClient : public ui::mojom::TextInputClient {
     if (run_loop_)
       run_loop_->Quit();
   }
+  void DispatchKeyEventPostIME(
+      std::unique_ptr<ui::Event> event,
+      const DispatchKeyEventPostIMECallback& callback) override {
+    callback.Run(false);
+  }
 
   mojo::Binding<ui::mojom::TextInputClient> binding_;
   std::unique_ptr<base::RunLoop> run_loop_;