Add WidgetTest::GetAllWidgets() to find dialogs created by TestBrowserDialog.

ui/views/test/widget_test.h

Index: ui/views/test/widget_test.h
diff --git a/ui/views/test/widget_test.h b/ui/views/test/widget_test.h
index 3eda5111b2b8af8e510d5ed6d7e9d7de8b1a930e..5ce2b6506466b29d23e006faa607780f312efd6f 100644
--- a/ui/views/test/widget_test.h
+++ b/ui/views/test/widget_test.h
@@ -90,6 +90,9 @@ class WidgetTest : public ViewsTestBase {
   // Return true if |window| is transparent according to the native platform.
   static bool IsNativeWindowTransparent(gfx::NativeWindow window);
 
+  // Returns the set of all Widgets that currently have a NativeWindow.
+  static Widget::Widgets GetAllWidgets();
+
  private:
   DISALLOW_COPY_AND_ASSIGN(WidgetTest);
 };