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

ui/views/test/widget_test_unittest.cc

+// Copyright 2017 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/views/test/widget_test.h"
+
+#include <algorithm>
+#include <vector>
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace views {
+namespace test {
+namespace {
+
+// Insert |widget| into |expected| and ensure it's reported by GetAllWidgets().
+void ExpectAdd(Widget::Widgets* expected, Widget* widget, const char* message) {
+  SCOPED_TRACE(message);
+  EXPECT_TRUE(expected->insert(widget).second);
+  Widget::Widgets actual = WidgetTest::GetAllWidgets();
+  EXPECT_EQ(expected->size(), actual.size());
+  EXPECT_TRUE(std::equal(expected->begin(), expected->end(), actual.begin()));
+}
+
+// Close |widgets[0]|, and expect all |widgets| to be removed.
+void ExpectClose(Widget::Widgets* expected,
+                 std::vector<Widget*> widgets,
+                 const char* message) {
+  SCOPED_TRACE(message);
+  for (Widget* widget : widgets)
+    EXPECT_EQ(1u, expected->erase(widget));
+  widgets[0]->CloseNow();
+  Widget::Widgets actual = WidgetTest::GetAllWidgets();
+  EXPECT_EQ(expected->size(), actual.size());
+  EXPECT_TRUE(std::equal(expected->begin(), expected->end(), actual.begin()));
+}
+
+}  // namespace
+
+using WidgetTestTest = WidgetTest;
+
+// Ensure that Widgets with various root windows are correctly reported by
+// WidgetTest::GetAllWidgets().
+TEST_F(WidgetTestTest, GetAllWidgets) {
+  Widget::Widgets expected;
+
+  EXPECT_EQ(expected, GetAllWidgets());
+
+  Widget* platform = CreateTopLevelPlatformWidget();
+  ExpectAdd(&expected, platform, "platform");

[sky, 2017/01/30 17:07:04]

It seems like the order of WidgetTest::GetAllWidgets() matches creation order.
Are you sure that is true? At least on windows I'm not sure EnumThreadWindow()
enumerates in any particular order.

[tapted, 2017/01/30 23:36:31]

Ah, it's coincidence here that |expected| is updated mostly LIFO order --
Widget::Widgets is a std::set, so the collections should be sorted by pointer
value. Added/updated comments.

+
+  Widget* platform_child = CreateChildPlatformWidget(platform->GetNativeView());
+  ExpectAdd(&expected, platform_child, "platform_child");
+
+  Widget* frameless = CreateTopLevelFramelessPlatformWidget();
+  ExpectAdd(&expected, frameless, "frameless");
+
+  Widget* native = CreateTopLevelNativeWidget();
+  ExpectAdd(&expected, native, "native");
+
+  Widget* native_child = CreateChildNativeWidgetWithParent(native);
+  ExpectAdd(&expected, native_child, "native_child");
+
+  Widget* desktop = CreateNativeDesktopWidget();
+  ExpectAdd(&expected, desktop, "desktop");
+
+  Widget* desktop_child = CreateChildNativeWidgetWithParent(desktop);
+  ExpectAdd(&expected, desktop_child, "desktop_child");
+
+  ExpectClose(&expected, {desktop, desktop_child}, "desktop");
+  ExpectClose(&expected, {native, native_child}, "native");
+  ExpectClose(&expected, {platform, platform_child}, "platform");
+  ExpectClose(&expected, {frameless}, "frameless");
+}
+
+}  // namespace views
+}  // namespace test