Fail tests that use ClickOnView() on an inactive window.

chrome/test/base/interactive_test_utils_cocoa.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/test/base/interactive_test_utils.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "chrome/app/chrome_command_ids.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_window.h"
 #import "chrome/browser/ui/cocoa/view_id_util.h"
+#include "testing/gtest/include/gtest/gtest.h"
 #include "ui/base/cocoa/cocoa_base_utils.h"
 
 namespace ui_test_utils {
 
 namespace {
 
 void MoveMouseToNSViewCenterAndPress(
     NSView* view,
     ui_controls::MouseButton button,
     int state,
@@ skipping 42 matching lines @@
     if (delegate == view)
       return true;
   }
 
   return false;
 }
 
 void ClickOnView(const Browser* browser, ViewID vid) {
   NSWindow* window = browser->window()->GetNativeWindow();
   DCHECK(window);
+  // Fail tests that use ClickOnView() on an inactive window. Tests that do will
+  // flake too easily. There seems to be no guarantee that the WindowServer will
+  // send the event to the window, or activate it. It isn't enough just to wait
+  // for NSWindowDidBecomeKeyNotification after this method.
+  EXPECT_TRUE([window isKeyWindow])
+      << "ClickOnView() in an inactive window is not robust.";
   NSView* view = view_id_util::GetView(window, vid);
   DCHECK(view);
   MoveMouseToNSViewCenterAndPress(
       view,
       ui_controls::LEFT,
       ui_controls::DOWN | ui_controls::UP,
       base::MessageLoop::QuitWhenIdleClosure());
   content::RunMessageLoop();
 }
 
 void FocusView(const Browser* browser, ViewID vid) {
    NSWindow* window = browser->window()->GetNativeWindow();
    DCHECK(window);
    NSView* view = view_id_util::GetView(window, vid);
    DCHECK(view);
    [window makeFirstResponder:view];
  }
 
 }  // namespace ui_test_utils