Fix positioning of Mac permission prompts when fullscreen.

ui/base/test/scoped_fake_nswindow_fullscreen.h

 // Copyright 2015 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.
 
 #ifndef UI_BASE_TEST_SCOPED_FAKE_NSWINDOW_FULLSCREEN_H_
 #define UI_BASE_TEST_SCOPED_FAKE_NSWINDOW_FULLSCREEN_H_
 
 #include <memory>
 
 #include "base/macros.h"
 
 namespace ui {
 namespace test {
 
 // Simulates fullscreen transitions on NSWindows. This allows testing fullscreen
 // logic without relying on the OS's fullscreen behavior as that tends to be
 // flaky, even in interactive tests. We only allow one NSWindow per process to
 // be fullscreen at a time, which should be sufficient for tests.
 class ScopedFakeNSWindowFullscreen {
  public:
   // Impl class to hide Obj-C implementation from this header.
   class Impl;
 
   ScopedFakeNSWindowFullscreen();
   ~ScopedFakeNSWindowFullscreen();
 
+  // Wait for any transition in progress to complete.
+  void FinishTransition();
+
  private:
   std::unique_ptr<Impl> impl_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedFakeNSWindowFullscreen);
 };
 
 }  // namespace test
 }  // namespace ui
 
 #endif  // UI_BASE_TEST_SCOPED_FAKE_NSWINDOW_FULLSCREEN_H_