Move WidgetActivationWaiter to a common place

ui/views/test/widget_test.cc

Index: ui/views/test/widget_test.cc
diff --git a/ui/views/test/widget_test.cc b/ui/views/test/widget_test.cc
index d67e951ce23eeba26abce4340ca8c3ce1216a796..457a63da806ba5eb6446b3b1e701611b12c4dc10 100644
--- a/ui/views/test/widget_test.cc
+++ b/ui/views/test/widget_test.cc
@@ -150,5 +150,32 @@ View* TestInitialFocusWidgetDelegate::GetInitiallyFocusedView() {
   return view_;
 }
 
+WidgetActivationWaiter::WidgetActivationWaiter(Widget* widget, bool active)
+    : observed_(false), active_(active) {
+  if (active == widget->IsActive()) {
+    observed_ = true;
+    return;
+  }
+  widget->AddObserver(this);
+}
+
+WidgetActivationWaiter::~WidgetActivationWaiter() {}
+
+void WidgetActivationWaiter::Wait() {
+  if (!observed_)
+    run_loop_.Run();
+}
+
+void WidgetActivationWaiter::OnWidgetActivationChanged(Widget* widget,
+                                                       bool active) {
+  if (active_ != active)
+    return;
+
+  observed_ = true;
+  widget->RemoveObserver(this);
+  if (run_loop_.running())
+    run_loop_.Quit();
+}
+
 }  // namespace test
 }  // namespace views