Chrome OS: Avoid GetAllWidgets in non-mash browser tests.

Avoid GetAllWidgets in classic ash and mus Chrome OS browser tests.
These configs cannot get a list of root windows at the Views layer.
Add a DCHECK to avoid using GetAllWidgets in those scenarios.

Win/Linux/Mac query their WMs directly for root windows; on Chrome OS:
1) Mash can use MusClient to get a list of root windows.
2) Unit tests can use AuraTestHelper to get the root window.
3) Non-mash browser tests must use ash::Shell to get root windows.

This should land after http://crrev.com/c/919922

Bug: 811940
Change-Id: I609531529ff5c4379f6c1de47ca878b30e7dd614
Reviewed-on: https://chromium-review.googlesource.com/922268Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Michael Wasserman <msw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537331}

chrome/browser/ui/test/test_browser_dialog.cc

@@ -164,17 +164,19 @@ bool TestBrowserDialog::AlwaysCloseAsynchronously() {
 }
 
 void TestBrowserDialog::UpdateWidgets() {
-#if defined(TOOLKIT_VIEWS)
-  widgets_ = views::test::WidgetTest::GetAllWidgets();
+  widgets_.clear();
 #if defined(OS_CHROMEOS)
-  // GetAllWidgets() uses AuraTestHelper to find the aura root window, but
-  // that's not used on browser_tests, so ask ash. Under mash the MusClient
-  // provides the list of root windows, so this isn't needed.
-  if (chromeos::GetAshConfig() != ash::Config::MASH) {
-    views::Widget::GetAllChildWidgets(ash::Shell::GetPrimaryRootWindow(),
-                                      &widgets_);
+  // Under mash, GetAllWidgets() uses MusClient to get the list of root windows.
+  // Otherwise, GetAllWidgets() relies on AuraTestHelper to get the root window,
+  // but that is not available in browser_tests, so use ash::Shell directly.
+  if (chromeos::GetAshConfig() == ash::Config::MASH) {
+    widgets_ = views::test::WidgetTest::GetAllWidgets();
+  } else {
+    for (aura::Window* root_window : ash::Shell::GetAllRootWindows())
+      views::Widget::GetAllChildWidgets(root_window, &widgets_);
   }
-#endif  // OS_CHROMEOS
+#elif defined(TOOLKIT_VIEWS)
+  widgets_ = views::test::WidgetTest::GetAllWidgets();
 #else
   NOTIMPLEMENTED();
 #endif

ui/views/test/widget_test_aura.cc

@@ -17,9 +17,6 @@
 #if defined(USE_X11)
 #include "ui/gfx/x/x11.h"        // nogncheck
 #include "ui/gfx/x/x11_types.h"  // nogncheck
-#endif
-
-#if defined(USE_X11)
 #include "ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h"
 #endif
 
@@ -75,22 +72,26 @@ std::vector<aura::Window*> GetAllTopLevelWindows() {
   std::vector<aura::Window*> roots;
 #if defined(USE_X11)
   roots = DesktopWindowTreeHostX11::GetAllOpenWindows();
-#endif
-#if defined(OS_WIN)
+#elif defined(OS_WIN)
   {
     FindAllWindowsData data = {&roots};
     EnumThreadWindows(GetCurrentThreadId(), FindAllWindowsCallback,
                       reinterpret_cast<LPARAM>(&data));
   }
-#endif  // OS_WIN
-  aura::test::AuraTestHelper* aura_test_helper =
-      aura::test::AuraTestHelper::GetInstance();
-  if (aura_test_helper)
-    roots.push_back(aura_test_helper->root_window());
-
+#endif
   if (MusClient::Get()) {
     auto mus_roots = MusClient::Get()->window_tree_client()->GetRoots();
     roots.insert(roots.end(), mus_roots.begin(), mus_roots.end());
+  } else {
+    aura::test::AuraTestHelper* aura_test_helper =
+        aura::test::AuraTestHelper::GetInstance();
+#if defined(OS_CHROMEOS)
+    // Chrome OS non-mash unit tests use AuraTestHelper to get the root window.
+    // Chrome OS non-mash browser tests must use ash::Shell::GetAllRootWindows.
+    DCHECK(aura_test_helper) << "Can't find all widgets without a test helper";
+#endif
+    if (aura_test_helper)
+      roots.push_back(aura_test_helper->root_window());
   }
   return roots;
 }