Fix flakiness in DesktopWindowTreeHostX11Test.InputMethodFocus

ActivationWaiter should be created as early as possible so that
PropertyNotify has time to be set before the widget is activated.

Otherwise, the waiter can miss that event, and the test times out.

Bug: 955316
Change-Id: I0e993e2aacdf8a2a97bfdeeeab75c7312c9259b0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2169886Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Maksim Sisov <msisov@igalia.com>
Cr-Commit-Position: refs/heads/master@{#763430}

ui/views/widget/desktop_aura/desktop_window_tree_host_x11_interactive_uitest.cc

@@ -234,6 +234,12 @@ TEST_F(DesktopWindowTreeHostX11Test, CaptureEventForwarding) {
 
 TEST_F(DesktopWindowTreeHostX11Test, InputMethodFocus) {
   std::unique_ptr<Widget> widget(CreateWidget(gfx::Rect(100, 100, 100, 100)));
+
+  // Waiter should be created as early as possible so that PropertyNotify has
+  // time to be set before widget is activated.
+  ActivationWaiter waiter(
+      widget->GetNativeWindow()->GetHost()->GetAcceleratedWidget());
+
   std::unique_ptr<Textfield> textfield(new Textfield);
   textfield->SetBounds(0, 0, 200, 20);
   widget->GetRootView()->AddChildView(textfield.get());
@@ -246,11 +252,6 @@ TEST_F(DesktopWindowTreeHostX11Test, InputMethodFocus) {
   // EXPECT_EQ(ui::TEXT_INPUT_TYPE_NONE,
   //           widget->GetInputMethod()->GetTextInputType());
 
-  // Waiter should be created before widget->Activate is called. Otherwise,
-  // there is a race, and waiter might not be able to set property changes mask
-  // on time and miss the events.
-  ActivationWaiter waiter(
-      widget->GetNativeWindow()->GetHost()->GetAcceleratedWidget());
   widget->Activate();
   waiter.Wait();