MacViews: Fix ViewTest.HandleAccelerator by faking window activation

ui/views/test/views_test_helper_mac.h

Index: ui/views/test/views_test_helper_mac.h
diff --git a/ui/views/test/views_test_helper_mac.h b/ui/views/test/views_test_helper_mac.h
index 31fc0d8d09289aa3220eb97e138729ec3b4719bb..6dbb253e0fa647c169b6e4254fa201a1bd639d1b 100644
--- a/ui/views/test/views_test_helper_mac.h
+++ b/ui/views/test/views_test_helper_mac.h
@@ -10,6 +10,9 @@
 #include "ui/views/test/views_test_helper.h"
 
 namespace ui {
+namespace test {
+class ScopedFakeNSWindowFocus;
+}
 class ScopedAnimationDurationScaleMode;
 }
 
@@ -21,12 +24,20 @@ class ViewsTestHelperMac : public ViewsTestHelper {
   ~ViewsTestHelperMac() override;
 
   // ViewsTestHelper:
+  void SetUp() override;
   void TearDown() override;
 
  private:
   // Disable animations during tests.
   scoped_ptr<ui::ScopedAnimationDurationScaleMode> zero_duration_mode_;
 
+  // When using desktop widgets on Mac, window activation is asynchronous
+  // because the window server is involved. A window may also be deactivated by
+  // a test running in parallel, making it flaky. In non-interactive/sharded
+  // tests, |faked_focus_| is initialized, permitting a unit test to "fake" this
+  // activation, causing it to be synchronous and per-process instead.
+  scoped_ptr<ui::test::ScopedFakeNSWindowFocus> faked_focus_;
+
   DISALLOW_COPY_AND_ASSIGN(ViewsTestHelperMac);
 };