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

chrome/test/base/interactive_test_utils_cocoa.mm

Index: chrome/test/base/interactive_test_utils_cocoa.mm
diff --git a/chrome/test/base/interactive_test_utils_cocoa.mm b/chrome/test/base/interactive_test_utils_cocoa.mm
index ee4e8c2da936b9515062ee4fa10c43511e27d684..df4de1af0f5cc1fc7409f9c79aa62cbe44c92708 100644
--- a/chrome/test/base/interactive_test_utils_cocoa.mm
+++ b/chrome/test/base/interactive_test_utils_cocoa.mm
@@ -13,6 +13,7 @@
 #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 {
@@ -75,6 +76,12 @@ bool IsViewFocused(const Browser* browser, ViewID vid) {
 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(