Mac: More robust "window under location" for interactive_ui_tests

ui/base/test/ui_controls_mac.mm

 // Copyright 2013 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 "ui/base/test/ui_controls.h"
 
 #import <Cocoa/Cocoa.h>
 #include <mach/mach_time.h>
 #include <vector>
 
@@ skipping 201 matching lines @@
 }
 
 // Returns the NSWindow located at |g_mouse_location|. NULL if there is no
 // window there, or if the window located there is not owned by the application.
 // On Mac, unless dragging, mouse events are sent to the window under the
 // cursor. Note that the OS will ignore transparent windows and windows that
 // explicitly ignore mouse events.
 NSWindow* WindowAtCurrentMouseLocation() {
   NSInteger window_number = [NSWindow windowNumberAtPoint:g_mouse_location
                               belowWindowWithWindowNumber:0];
-  return
+  NSWindow* window =
       [[NSApplication sharedApplication] windowWithWindowNumber:window_number];
+  if (window)
+    return window;
+
+  // It's possible for a window owned by another application to be at that
+  // location. Cocoa won't provide an NSWindow* for those. Tests should not care
+  // about other applications, and raising windows in a headless application is
+  // flaky due to OS restrictions. For tests, hunt through all of this
+  // application's windows, top to bottom, looking for a good candidate.
+  NSArray* window_list = [[NSApplication sharedApplication] orderedWindows];
+  for (window in window_list) {
+    // Note this skips the extra checks (e.g. fully-transparent windows), that
+    // +[NSWindow windowNumberAtPoint:] performs. Tests that care about that
+    // should check separately (the goal here is to minimize flakiness).
+    if (NSPointInRect(g_mouse_location, [window frame]))
+      return window;
+  }
+
+  // Note that -[NSApplication orderedWindows] won't include NSPanels. If a test
+  // uses those, it will need to handle that itself.
+  return nil;
 }
 
 }  // namespace
 
 namespace ui_controls {
 
 void EnableUIControls() {
   g_ui_controls_enabled = true;
 }
 
@@ skipping 153 matching lines @@
 void RunClosureAfterAllPendingUIEvents(const base::Closure& closure) {
   base::MessageLoop::current()->PostTask(
       FROM_HERE, base::Bind(&EventQueueWatcher, closure));
 }
 
 bool IsFullKeyboardAccessEnabled() {
   return [NSApp isFullKeyboardAccessEnabled];
 }
 
 }  // namespace ui_controls