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..f068fd35a6b0a90d8774a16589ae7828a1e10f5c 100644
--- a/ui/views/test/widget_test.cc
+++ b/ui/views/test/widget_test.cc
@@ -150,5 +150,45 @@ View* TestInitialFocusWidgetDelegate::GetInitiallyFocusedView() {
   return view_;
 }
 
+WidgetActivationWaiter::WidgetActivationWaiter(Widget* widget, bool active)
+    : observed_(false), active_(active) {
+#if defined(OS_WIN)
+  // On Windows, a HWND can receive a WM_ACTIVATE message without the value
+  // of ::GetActiveWindow() updating to reflect that change. This can cause
+  // the active window reported by IsActive() to get out of sync. Usually this
+  // happens after a call to HWNDMessageHandler::Deactivate() which works by
+  // activating some other window, which might be in another application.
+  // Doing this can trigger the native OS activation-blocker, causing the
+  // taskbar icon to flash instead. But since activation of native widgets on
+  // Windows is synchronous, we never have to wait anyway, so it's safe to
+  // return here.
+  if (active == widget->IsActive()) {
+    observed_ = true;
+    return;
+  }
+#endif
+  // Always expect a change for tests using this.
+  EXPECT_NE(active, widget->IsActive());

[sky, 2016/10/12 16:05:43]

I think this is error prone for a general class. You should remove the ifdef
above for all platforms.

[Qiang(Joe) Xu, 2016/10/12 16:55:58]

Done.

+  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