Accessibility checks flag warning tray crash fix

Bug: 819350
Change-Id: I75abdd3988c0c6ff3e73e67bc8fdef30e05b6aae
Reviewed-on: https://chromium-review.googlesource.com/964246
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544088}

ash/system/flag_warning/flag_warning_tray.cc

@@ -37,21 +37,22 @@ FlagWarningTray::FlagWarningTray(Shelf* shelf) : shelf_(shelf) {
   DCHECK(shelf_);
   SetLayoutManager(std::make_unique<views::FillLayout>());
 
-  const bool is_mash = Shell::GetAshConfig() == Config::MASH;
-  if (is_mash) {
-    container_ = new TrayContainer(shelf);
-    AddChildView(container_);
-
-    button_ = views::MdTextButton::Create(this, base::string16(),
-                                          CONTEXT_LAUNCHER_BUTTON);
-    button_->SetProminent(true);
-    button_->SetBgColorOverride(gfx::kGoogleYellow300);
-    button_->SetEnabledTextColors(SK_ColorBLACK);
-    button_->SetTooltipText(base::ASCIIToUTF16(kTooltipText));
-    UpdateButton();
-    container_->AddChildView(button_);
-  }
-  SetVisible(is_mash);
+  // Flag warning tray is not currently used in non-MASH environments, because
+  // mus will roll out via experiment/Finch trial and showing the tray would
+  // reveal the experiment state to users.
+  DCHECK_EQ(Shell::GetAshConfig(), Config::MASH);
+  container_ = new TrayContainer(shelf);
+  AddChildView(container_);
+
+  button_ = views::MdTextButton::Create(this, base::string16(),
+                                        CONTEXT_LAUNCHER_BUTTON);
+  button_->SetProminent(true);
+  button_->SetBgColorOverride(gfx::kGoogleYellow300);
+  button_->SetEnabledTextColors(SK_ColorBLACK);
+  button_->SetTooltipText(base::ASCIIToUTF16(kTooltipText));
+  UpdateButton();
+  container_->AddChildView(button_);
+  SetVisible(true);
 }
 
 FlagWarningTray::~FlagWarningTray() = default;

ash/system/flag_warning/flag_warning_tray_unittest.cc

@@ -16,18 +16,14 @@ namespace {
 using FlagWarningTrayTest = AshTestBase;
 
 TEST_F(FlagWarningTrayTest, Visibility) {
-  // Tray is always created.
-  FlagWarningTray* tray = Shell::GetPrimaryRootWindowController()
-                              ->GetStatusAreaWidget()
-                              ->flag_warning_tray_for_testing();
-  ASSERT_TRUE(tray);
-
-  // Warning should be visible in ash_unittests when mash is enabled, but not in
-  // regular ash_unittests. The warning does not show for Config::MUS because
+  // Flag warning tray is not currently used in non-MASH environments, because
   // mus will roll out via experiment/Finch trial and showing the tray would
   // reveal the experiment state to users.
   const bool is_mash = Shell::GetAshConfig() == Config::MASH;
-  EXPECT_EQ(tray->visible(), is_mash);
+  FlagWarningTray* tray = Shell::GetPrimaryRootWindowController()
+                              ->GetStatusAreaWidget()
+                              ->flag_warning_tray_for_testing();
+  EXPECT_EQ(tray != nullptr, is_mash);
 }
 
 }  // namespace

ash/system/status_area_widget.cc

@@ -5,6 +5,7 @@
 #include "ash/system/status_area_widget.h"
 
 #include "ash/public/cpp/ash_features.h"
+#include "ash/public/cpp/config.h"
 #include "ash/session/session_controller.h"
 #include "ash/shelf/shelf.h"
 #include "ash/shell.h"
@@ -71,8 +72,13 @@ void StatusAreaWidget::Initialize() {
   logout_button_tray_ = std::make_unique<LogoutButtonTray>(shelf_);
   status_area_widget_delegate_->AddChildView(logout_button_tray_.get());
 
-  flag_warning_tray_ = std::make_unique<FlagWarningTray>(shelf_);
-  status_area_widget_delegate_->AddChildView(flag_warning_tray_.get());
+  if (Shell::GetAshConfig() == ash::Config::MASH) {
+    // Flag warning tray is not currently used in non-MASH environments, because
+    // mus will roll out via experiment/Finch trial and showing the tray would
+    // reveal the experiment state to users.
+    flag_warning_tray_ = std::make_unique<FlagWarningTray>(shelf_);
+    status_area_widget_delegate_->AddChildView(flag_warning_tray_.get());
+  }
 
   // The layout depends on the number of children, so build it once after
   // adding all of them.
@@ -119,7 +125,8 @@ void StatusAreaWidget::UpdateAfterShelfAlignmentChange() {
   ime_menu_tray_->UpdateAfterShelfAlignmentChange();
   palette_tray_->UpdateAfterShelfAlignmentChange();
   overview_button_tray_->UpdateAfterShelfAlignmentChange();
-  flag_warning_tray_->UpdateAfterShelfAlignmentChange();
+  if (flag_warning_tray_)
+    flag_warning_tray_->UpdateAfterShelfAlignmentChange();
   status_area_widget_delegate_->UpdateLayout();
 }
 
@@ -176,7 +183,8 @@ void StatusAreaWidget::SchedulePaint() {
   ime_menu_tray_->SchedulePaint();
   palette_tray_->SchedulePaint();
   overview_button_tray_->SchedulePaint();
-  flag_warning_tray_->SchedulePaint();
+  if (flag_warning_tray_)
+    flag_warning_tray_->SchedulePaint();
 }
 
 const ui::NativeTheme* StatusAreaWidget::GetNativeTheme() const {