CrOS Shelf: Unify ways of checking tablet mode

Bug: None
Change-Id: Ie5ce5db5a2dfb13f96ab370102f9f1f56782d663
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2049949Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Commit-Queue: Manu Cornet <manucornet@chromium.org>
Cr-Commit-Position: refs/heads/master@{#741094}

ash/home_screen/home_launcher_gesture_handler.cc

@@ -61,17 +61,13 @@ constexpr int kScrollVelocityThreshold = 6;
 // this ratio.
 constexpr float kWidthRatio = 0.8f;
 
-bool IsTabletMode() {
-  return Shell::Get()->tablet_mode_controller()->InTabletMode();
-}
-
 // Checks if |window| can be hidden or shown with a gesture.
 bool CanProcessWindow(aura::Window* window,
                       HomeLauncherGestureHandler::Mode mode) {
   if (!window)
     return false;
 
-  if (!IsTabletMode())
+  if (!Shell::Get()->IsInTabletMode())
     return false;
 
   if (!window->IsVisible() &&
@@ -769,7 +765,7 @@ bool HomeLauncherGestureHandler::SetUpWindows(Mode mode, aura::Window* window) {
     return false;
   }
 
-  if (IsTabletMode() && overview_active_on_gesture_start_ &&
+  if (Shell::Get()->IsInTabletMode() && overview_active_on_gesture_start_ &&
       !split_view_active && mode == Mode::kSlideUpToShow) {
     active_window_.reset();
     return true;
@@ -936,7 +932,7 @@ bool HomeLauncherGestureHandler::OnDragEnded(const gfx::PointF& location,
   } else {
     // In clamshell mode, AppListView::SetIsInDrag is called explicitly so it
     // does not need the notification from HomeLauncherGestureHandler.
-    if (IsTabletMode()) {
+    if (Shell::Get()->IsInTabletMode()) {
       HomeScreenDelegate* home_screen_delegate = GetHomeScreenDelegate();
       DCHECK(home_screen_delegate);
       home_screen_delegate->OnHomeLauncherDragEnd();

ash/shelf/home_button_controller.cc

@@ -34,7 +34,7 @@ constexpr base::TimeDelta kAssistantAnimationDelay =
 
 // Returns true if the button should appear activatable.
 bool CanActivate() {
-  return Shell::Get()->tablet_mode_controller()->InTabletMode() ||
+  return Shell::Get()->IsInTabletMode() ||
          !Shell::Get()->app_list_controller()->IsVisible();
 }
 
@@ -178,7 +178,7 @@ void HomeButtonController::StartAssistantAnimation() {
 void HomeButtonController::OnAppListShown() {
   // Do not show a highlight in tablet mode, since the home screen view is
   // always open in the background.
-  if (!Shell::Get()->tablet_mode_controller()->InTabletMode())
+  if (!Shell::Get()->IsInTabletMode())
     button_->AnimateInkDrop(views::InkDropState::ACTIVATED, nullptr);
   is_showing_app_list_ = true;
   RootWindowController::ForWindow(button_->GetWidget()->GetNativeWindow())

ash/shelf/scrollable_shelf_view.cc

@@ -114,17 +114,6 @@ int GetGestureDragThreshold() {
   return ShelfConfig::Get()->button_size() / 2;
 }
 
-bool IsInTabletMode() {
-  TabletModeController* tablet_mode_controller =
-      Shell::Get()->tablet_mode_controller();
-
-  // TabletModeController is destructed before ScrollableShelfView.
-  if (!tablet_mode_controller || !tablet_mode_controller->InTabletMode())
-    return false;
-
-  return true;
-}
-
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -332,7 +321,7 @@ class ScrollableShelfAnimationMetricsReporter
   // ui::AnimationMetricsReporter:
   void Report(int value) override {
     base::UmaHistogramPercentage(kAnimationSmoothnessHistogram, value);
-    if (IsInTabletMode()) {
+    if (Shell::Get()->IsInTabletMode()) {
       if (Shell::Get()->app_list_controller()->IsVisible()) {
         base::UmaHistogramPercentage(
             kAnimationSmoothnessTabletLauncherVisibleHistogram, value);
@@ -550,12 +539,14 @@ void ScrollableShelfView::OnFocusRingActivationChanged(bool activated) {
   if (activated) {
     focus_ring_activated_ = true;
     SetPaneFocusAndFocusDefault();
-    if (IsInTabletMode() && chromeos::switches::ShouldShowShelfHotseat())
+    if (Shell::Get()->IsInTabletMode() &&
+        chromeos::switches::ShouldShowShelfHotseat())
       GetShelf()->shelf_widget()->ForceToShowHotseat();
   } else {
     // Shows the gradient shader when the focus ring is disabled.
     focus_ring_activated_ = false;
-    if (IsInTabletMode() && chromeos::switches::ShouldShowShelfHotseat())
+    if (Shell::Get()->IsInTabletMode() &&
+        chromeos::switches::ShouldShowShelfHotseat())
       GetShelf()->shelf_widget()->ForceToHideHotseat();
   }
 
@@ -1084,7 +1075,8 @@ void ScrollableShelfView::OnShelfButtonAboutToRequestFocusFromTabTraversal(
   ShelfWidget* shelf_widget = GetShelf()->shelf_widget();
   // In tablet mode, when the hotseat is not extended but one of the buttons
   // gets focused, it should update the visibility of the hotseat.
-  if (IsInTabletMode() && chromeos::switches::ShouldShowShelfHotseat() &&
+  if (Shell::Get()->IsInTabletMode() &&
+      chromeos::switches::ShouldShowShelfHotseat() &&
       !shelf_widget->hotseat_widget()->IsExtended()) {
     shelf_widget->shelf_layout_manager()->UpdateVisibilityState();
   }
@@ -1103,7 +1095,8 @@ void ScrollableShelfView::ButtonPressed(views::Button* sender,
 
 void ScrollableShelfView::HandleAccessibleActionScrollToMakeVisible(
     ShelfButton* button) {
-  if (IsInTabletMode() && chromeos::switches::ShouldShowShelfHotseat()) {
+  if (Shell::Get()->IsInTabletMode() &&
+      chromeos::switches::ShouldShowShelfHotseat()) {
     // Only in tablet mode with hotseat enabled, may scrollable shelf be hidden.
     GetShelf()->shelf_widget()->ForceToShowHotseat();
   }
@@ -1485,7 +1478,7 @@ bool ScrollableShelfView::ProcessGestureEvent(const ui::GestureEvent& event) {
   // end.
   if (event.type() == ui::ET_GESTURE_SCROLL_BEGIN) {
     DCHECK(!presentation_time_recorder_);
-    if (IsInTabletMode()) {
+    if (Shell::Get()->IsInTabletMode()) {
       if (Shell::Get()->app_list_controller()->IsVisible()) {
         presentation_time_recorder_ = CreatePresentationTimeHistogramRecorder(
             GetWidget()->GetCompositor(),
@@ -2004,8 +1997,8 @@ void ScrollableShelfView::UpdateAvailableSpace() {
 
 gfx::Rect ScrollableShelfView::CalculateVisibleSpace(
     LayoutStrategy layout_strategy) const {
-  const bool in_hotseat_tablet =
-      chromeos::switches::ShouldShowShelfHotseat() && IsInTabletMode();
+  const bool in_hotseat_tablet = chromeos::switches::ShouldShowShelfHotseat() &&
+                                 Shell::Get()->IsInTabletMode();
   if (layout_strategy == kNotShowArrowButtons && !in_hotseat_tablet)
     return GetAvailableLocalBounds(/*use_target_bounds=*/false);
 
@@ -2040,8 +2033,8 @@ gfx::Rect ScrollableShelfView::CalculateVisibleSpace(
 
 gfx::Insets ScrollableShelfView::CalculateRipplePaddingInsets() const {
   // Indicates whether it is in tablet mode with hotseat enabled.
-  const bool in_hotseat_tablet =
-      chromeos::switches::ShouldShowShelfHotseat() && IsInTabletMode();
+  const bool in_hotseat_tablet = chromeos::switches::ShouldShowShelfHotseat() &&
+                                 Shell::Get()->IsInTabletMode();
 
   const int ripple_padding =
       ShelfConfig::Get()->scrollable_shelf_ripple_padding();
@@ -2060,7 +2053,8 @@ gfx::Insets ScrollableShelfView::CalculateRipplePaddingInsets() const {
 
 gfx::RoundedCornersF
 ScrollableShelfView::CalculateShelfContainerRoundedCorners() const {
-  if (!chromeos::switches::ShouldShowShelfHotseat() || !IsInTabletMode())
+  if (!chromeos::switches::ShouldShowShelfHotseat() ||
+      !Shell::Get()->IsInTabletMode())
     return gfx::RoundedCornersF();
 
   const bool is_horizontal_alignment = GetShelf()->IsHorizontalAlignment();

ash/shelf/shelf_config.cc

@@ -27,12 +27,6 @@ namespace {
 // dense shelf will be active.
 const int kDenseShelfScreenSizeThreshold = 600;
 
-// Returns whether tablet mode is currently active.
-bool IsTabletMode() {
-  return Shell::Get()->tablet_mode_controller() &&
-         Shell::Get()->tablet_mode_controller()->InTabletMode();
-}
-
 // Whether the the shelf control buttons must be shown for accessibility
 // reasons.
 bool ShelfControlsForcedShownForAccessibility() {
@@ -185,7 +179,8 @@ int ShelfConfig::system_shelf_size() const {
 }
 
 int ShelfConfig::hotseat_size() const {
-  if (!chromeos::switches::ShouldShowShelfHotseat() || !IsTabletMode()) {
+  if (!chromeos::switches::ShouldShowShelfHotseat() ||
+      !Shell::Get()->IsInTabletMode()) {
     return shelf_size();
   }
   return is_dense_ ? 48 : 56;
@@ -211,7 +206,7 @@ int ShelfConfig::control_size() const {
   if (!chromeos::switches::ShouldShowShelfHotseat())
     return 40;
 
-  if (!IsTabletMode())
+  if (!Shell::Get()->IsInTabletMode())
     return 36;
 
   return is_dense_ ? 36 : 40;
@@ -219,7 +214,7 @@ int ShelfConfig::control_size() const {
 
 int ShelfConfig::control_border_radius() const {
   return (chromeos::switches::ShouldShowShelfHotseat() && is_in_app() &&
-          IsTabletMode())
+          Shell::Get()->IsInTabletMode())
              ? control_size() / 2 - in_app_control_button_height_inset_
              : control_size() / 2;
 }
@@ -230,7 +225,7 @@ int ShelfConfig::overflow_button_margin() const {
 
 int ShelfConfig::control_button_edge_spacing(bool is_primary_axis_edge) const {
   if (is_primary_axis_edge)
-    return IsTabletMode() ? 8 : 6;
+    return Shell::Get()->IsInTabletMode() ? 8 : 6;
 
   return (shelf_size() - control_size()) / 2;
 }
@@ -265,7 +260,7 @@ void ShelfConfig::UpdateConfig(bool app_list_visible) {
   const gfx::Rect screen_size =
       display::Screen::GetScreen()->GetPrimaryDisplay().bounds();
 
-  const bool in_tablet_mode = IsTabletMode();
+  const bool in_tablet_mode = Shell::Get()->IsInTabletMode();
   const bool new_is_dense =
       chromeos::switches::ShouldShowShelfHotseat() &&
       (!in_tablet_mode ||
@@ -297,7 +292,7 @@ int ShelfConfig::GetShelfSize(bool ignore_in_app_state) const {
     return 56;
 
   // In clamshell mode, the shelf always has the same size.
-  if (!IsTabletMode())
+  if (!Shell::Get()->IsInTabletMode())
     return 48;
 
   if (!ignore_in_app_state && is_in_app())
@@ -310,7 +305,8 @@ SkColor ShelfConfig::GetShelfControlButtonColor() const {
   const session_manager::SessionState session_state =
       Shell::Get()->session_controller()->GetSessionState();
 
-  if (chromeos::switches::ShouldShowShelfHotseat() && IsTabletMode() &&
+  if (chromeos::switches::ShouldShowShelfHotseat() &&
+      Shell::Get()->IsInTabletMode() &&
       session_state == session_manager::SessionState::ACTIVE) {
     return is_in_app() ? SK_ColorTRANSPARENT : GetDefaultShelfColor();
   } else if (session_state == session_manager::SessionState::OOBE) {
@@ -359,10 +355,10 @@ SkColor ShelfConfig::GetDefaultShelfColor() const {
 
   AshColorProvider::BaseLayerType layer_type;
   if (!chromeos::switches::ShouldShowShelfHotseat()) {
-    layer_type = IsTabletMode()
+    layer_type = Shell::Get()->IsInTabletMode()
                      ? AshColorProvider::BaseLayerType::kTransparent60
                      : AshColorProvider::BaseLayerType::kTransparent80;
-  } else if (IsTabletMode()) {
+  } else if (Shell::Get()->IsInTabletMode()) {
     layer_type = is_in_app() ? AshColorProvider::BaseLayerType::kTransparent90
                              : AshColorProvider::BaseLayerType::kTransparent60;
   } else {
@@ -377,15 +373,16 @@ SkColor ShelfConfig::GetDefaultShelfColor() const {
 
 int ShelfConfig::GetShelfControlButtonBlurRadius() const {
   if (features::IsBackgroundBlurEnabled() &&
-      chromeos::switches::ShouldShowShelfHotseat() && IsTabletMode() &&
-      !is_in_app()) {
+      chromeos::switches::ShouldShowShelfHotseat() &&
+      Shell::Get()->IsInTabletMode() && !is_in_app()) {
     return shelf_blur_radius_;
   }
   return 0;
 }
 
 int ShelfConfig::GetAppIconEndPadding() const {
-  return (chromeos::switches::ShouldShowShelfHotseat() && IsTabletMode())
+  return (chromeos::switches::ShouldShowShelfHotseat() &&
+          Shell::Get()->IsInTabletMode())
              ? app_icon_end_padding_
              : 0;
 }

ash/shelf/shelf_control_button.cc

@@ -42,8 +42,7 @@ class ShelfControlButtonHighlightPathGenerator
     visual_bounds.ClampToCenteredSize(
         gfx::SizeF(shelf_config->control_size(), shelf_config->control_size()));
     if (chromeos::switches::ShouldShowShelfHotseat() &&
-        Shell::Get()->tablet_mode_controller()->InTabletMode() &&
-        shelf_config->is_in_app()) {
+        Shell::Get()->IsInTabletMode() && shelf_config->is_in_app()) {
       visual_bounds.Inset(0,
                           shelf_config->in_app_control_button_height_inset());
     }

ash/shelf/shelf_layout_manager.cc

@@ -42,7 +42,6 @@
 #include "ash/wm/overview/overview_controller.h"
 #include "ash/wm/screen_pinning_controller.h"
 #include "ash/wm/splitview/split_view_controller.h"
-#include "ash/wm/tablet_mode/tablet_mode_controller.h"
 #include "ash/wm/window_state.h"
 #include "ash/wm/window_util.h"
 #include "ash/wm/work_area_insets.h"
@@ -139,15 +138,9 @@ bool IsAppListWindow(const aura::Window* window) {
   return parent && parent->id() == kShellWindowId_AppListContainer;
 }
 
-bool IsTabletModeEnabled() {
-  // Shell could be destroying. Shell destroys TabletModeController before
-  // closing all windows.
-  return Shell::Get()->tablet_mode_controller() &&
-         Shell::Get()->tablet_mode_controller()->InTabletMode();
-}
-
 bool IsHotseatEnabled() {
-  return IsTabletModeEnabled() && chromeos::switches::ShouldShowShelfHotseat();
+  return Shell::Get()->IsInTabletMode() &&
+         chromeos::switches::ShouldShowShelfHotseat();
 }
 
 int GetOffset(int offset, bool from_touchpad) {
@@ -197,7 +190,7 @@ int GetShelfInset(ShelfVisibilityState visibility_state, int size) {
 // window.
 aura::Window* GetWindowForDragToHomeOrOverview(
     const gfx::Point& location_in_screen) {
-  if (!IsTabletModeEnabled())
+  if (!Shell::Get()->IsInTabletMode())
     return nullptr;
 
   auto mru_windows =
@@ -475,7 +468,8 @@ gfx::Rect ShelfLayoutManager::GetIdealBounds() const {
 }
 
 gfx::Rect ShelfLayoutManager::GetIdealBoundsForWorkAreaCalculation() const {
-  if (!IsTabletModeEnabled() || !chromeos::switches::ShouldShowShelfHotseat() ||
+  if (!Shell::Get()->IsInTabletMode() ||
+      !chromeos::switches::ShouldShowShelfHotseat() ||
       state_.session_state != session_manager::SessionState::ACTIVE) {
     return GetIdealBounds();
   }
@@ -787,7 +781,7 @@ ShelfBackgroundType ShelfLayoutManager::GetShelfBackgroundType() const {
   const bool in_overview =
       Shell::Get()->overview_controller() &&
       Shell::Get()->overview_controller()->InOverviewSession();
-  if (IsTabletModeEnabled()) {
+  if (Shell::Get()->IsInTabletMode()) {
     if (app_list_is_visible) {
       // If the home launcher is shown or mostly shown, show the home launcher
       // background. If it is mostly hidden, show the in-app or overview
@@ -819,7 +813,8 @@ ShelfBackgroundType ShelfLayoutManager::GetShelfBackgroundType() const {
     // When a window is maximized, if the auto-hide shelf is enabled and we are
     // in clamshell mode, the shelf will keep the default transparent
     // background.
-    if (!IsTabletModeEnabled() && state_.visibility_state == SHELF_AUTO_HIDE)
+    if (!Shell::Get()->IsInTabletMode() &&
+        state_.visibility_state == SHELF_AUTO_HIDE)
       return ShelfBackgroundType::kDefaultBg;
 
     return ShelfBackgroundType::kMaximized;
@@ -1583,7 +1578,7 @@ void ShelfLayoutManager::UpdateBoundsAndOpacity(bool animate) {
 bool ShelfLayoutManager::IsDraggingWindowFromTopOrCaptionArea() const {
   // Currently dragging maximized or fullscreen window from the top or the
   // caption area is only allowed in tablet mode.
-  if (!IsTabletModeEnabled())
+  if (!Shell::Get()->IsInTabletMode())
     return false;
 
   // TODO(minch): Check active window directly if removed search field
@@ -1865,7 +1860,7 @@ ShelfAutoHideState ShelfLayoutManager::CalculateAutoHideState(
   if (shelf_->auto_hide_lock())
     return state_.auto_hide_state;
 
-  const bool in_tablet_mode = IsTabletModeEnabled();
+  const bool in_tablet_mode = Shell::Get()->IsInTabletMode();
   // Don't let the shelf auto-hide when in tablet mode and Chromevox is on.
   if (in_tablet_mode &&
       Shell::Get()->accessibility_controller()->spoken_feedback_enabled()) {
@@ -1937,7 +1932,7 @@ base::Optional<ShelfAutoHideState>
 ShelfLayoutManager::CalculateAutoHideStateBasedOnCursorLocation() const {
   // No mouse is available in tablet mode. So there is no point to calculate
   // the auto-hide state by the cursor location in this scenario.
-  const bool in_tablet_mode = IsTabletModeEnabled();
+  const bool in_tablet_mode = Shell::Get()->IsInTabletMode();
   if (in_tablet_mode)
     return base::nullopt;
 
@@ -2023,7 +2018,8 @@ void ShelfLayoutManager::UpdateShelfVisibilityAfterLoginUIChange() {
 float ShelfLayoutManager::ComputeTargetOpacity(const State& state) const {
   // The shelf should not become transparent during the animation to or from
   // HomeLauncher.
-  if (chromeos::switches::ShouldShowShelfHotseat() && IsTabletModeEnabled() &&
+  if (chromeos::switches::ShouldShowShelfHotseat() &&
+      Shell::Get()->IsInTabletMode() &&
       Shell::Get()->app_list_controller()->home_launcher_transition_state() !=
           AppListControllerImpl::HomeLauncherTransitionState::kFinished) {
     return 1.0f;
@@ -2054,7 +2050,7 @@ float ShelfLayoutManager::ComputeTargetOpacity(const State& state) const {
 bool ShelfLayoutManager::IsShelfHiddenForFullscreen() const {
   // If the non-fullscreen app list should be shown, the shelf should not be
   // hidden.
-  if (!IsTabletModeEnabled() &&
+  if (!Shell::Get()->IsInTabletMode() &&
       Shell::Get()->app_list_controller()->GetTargetVisibility()) {
     return false;
   }
@@ -2258,7 +2254,7 @@ bool ShelfLayoutManager::StartAppListDrag(
     float scroll_y_hint) {
   // If the home screen is available, gesture dragging is handled by
   // HomeLauncherGestureHandler.
-  if (IsTabletModeEnabled() && event_in_screen.IsGestureEvent())
+  if (Shell::Get()->IsInTabletMode() && event_in_screen.IsGestureEvent())
     return false;
 
   // Fullscreen app list can only be dragged from bottom alignment shelf.
@@ -2304,7 +2300,7 @@ bool ShelfLayoutManager::StartShelfDrag(const ui::LocatedEvent& event_in_screen,
                                         const gfx::Vector2dF& scroll_hint) {
   // Disable the shelf dragging if the fullscreen app list is opened.
   if (Shell::Get()->app_list_controller()->IsVisible() &&
-      !IsTabletModeEnabled())
+      !Shell::Get()->IsInTabletMode())
     return false;
 
   // Also disable shelf drags until the overflow shelf is closed.
@@ -2430,7 +2426,8 @@ void ShelfLayoutManager::CompleteDrag(const ui::LocatedEvent& event_in_screen) {
     window_drag_controller_->FinalizeDraggedWindow();
 
   // Hotseat gestures are meaningful only in tablet mode with hotseat enabled.
-  if (chromeos::switches::ShouldShowShelfHotseat() && IsTabletModeEnabled()) {
+  if (chromeos::switches::ShouldShowShelfHotseat() &&
+      Shell::Get()->IsInTabletMode()) {
     base::Optional<InAppShelfGestures> gesture_to_record =
         CalculateHotseatGestureToRecord(window_drag_result,
                                         transitioned_from_overview_to_home,
@@ -2643,7 +2640,7 @@ bool ShelfLayoutManager::MaybeStartDragWindowFromShelf(
     const gfx::Vector2dF& scroll) {
   if (!features::IsDragFromShelfToHomeOrOverviewEnabled())
     return false;
-  if (!IsTabletModeEnabled())
+  if (!Shell::Get()->IsInTabletMode())
     return false;
   if (drag_status_ != kDragInProgress)
     return false;

ash/shelf/shelf_navigation_widget.cc

@@ -33,11 +33,6 @@ namespace {
 constexpr base::TimeDelta kButtonOpacityAnimationDuration =
     base::TimeDelta::FromMilliseconds(50);
 
-bool IsTabletMode() {
-  return Shell::Get()->tablet_mode_controller() &&
-         Shell::Get()->tablet_mode_controller()->InTabletMode();
-}
-
 // Returns the bounds for the first button shown in this view (the back
 // button in tablet mode, the home button otherwise).
 gfx::Rect GetFirstButtonBounds(bool is_shelf_horizontal) {
@@ -68,8 +63,8 @@ bool IsBackButtonShown() {
   if (!ShelfConfig::Get()->shelf_controls_shown())
     return false;
   return chromeos::switches::ShouldShowShelfHotseat()
-             ? IsTabletMode() && ShelfConfig::Get()->is_in_app()
-             : IsTabletMode();
+             ? Shell::Get()->IsInTabletMode() && ShelfConfig::Get()->is_in_app()
+             : Shell::Get()->IsInTabletMode();
 }
 
 bool IsHomeButtonShown() {
@@ -185,8 +180,8 @@ void ShelfNavigationWidget::Delegate::UpdateOpaqueBackground() {
     return;
   }
 
-  if (chromeos::switches::ShouldShowShelfHotseat() && IsTabletMode() &&
-      ShelfConfig::Get()->is_in_app()) {
+  if (chromeos::switches::ShouldShowShelfHotseat() &&
+      Shell::Get()->IsInTabletMode() && ShelfConfig::Get()->is_in_app()) {
     opaque_background_.SetVisible(false);
     return;
   }
@@ -477,7 +472,8 @@ void ShelfNavigationWidget::UpdateTargetBoundsForGesture() {
   const gfx::Point shelf_origin =
       shelf_->shelf_widget()->GetTargetBounds().origin();
   if (shelf_->IsHorizontalAlignment()) {
-    if (!IsTabletMode() || !chromeos::switches::ShouldShowShelfHotseat()) {
+    if (!Shell::Get()->IsInTabletMode() ||
+        !chromeos::switches::ShouldShowShelfHotseat()) {
       target_bounds_.set_y(shelf_origin.y() +
                            ShelfConfig::Get()->button_spacing());
     }

ash/shelf/shelf_widget.cc

@@ -74,11 +74,6 @@ views::View* FindFirstOrLastFocusableChild(views::View* root,
       &dummy_focus_traversable, &dummy_focus_traversable_view);
 }
 
-bool IsInTabletMode() {
-  return Shell::Get()->tablet_mode_controller() &&
-         Shell::Get()->tablet_mode_controller()->InTabletMode();
-}
-
 }  // namespace
 
 // The contents view of the Shelf. In an active session, this is used to
@@ -304,7 +299,7 @@ void ShelfWidget::DelegateView::UpdateOpaqueBackground() {
   const Shelf* shelf = shelf_widget_->shelf();
   const ShelfBackgroundType background_type =
       shelf_widget_->GetBackgroundType();
-  const bool tablet_mode = IsInTabletMode();
+  const bool tablet_mode = Shell::Get()->IsInTabletMode();
   const bool in_app = ShelfConfig::Get()->is_in_app();
 
   bool show_opaque_background =
@@ -350,7 +345,7 @@ void ShelfWidget::DelegateView::UpdateOpaqueBackground() {
 }
 
 void ShelfWidget::DelegateView::UpdateDragHandle() {
-  if (!IsInTabletMode() || !ShelfConfig::Get()->is_in_app() ||
+  if (!Shell::Get()->IsInTabletMode() || !ShelfConfig::Get()->is_in_app() ||
       !chromeos::switches::ShouldShowShelfHotseat() ||
       hide_background_for_transitions_) {
     drag_handle_->SetVisible(false);
@@ -588,7 +583,7 @@ void ShelfWidget::RegisterHotseatWidget(HotseatWidget* hotseat_widget) {
 
 void ShelfWidget::OnTabletModeChanged() {
   // Resets |is_hotseat_forced_to_show| when leaving the tablet mode.
-  if (!IsInTabletMode())
+  if (!Shell::Get()->IsInTabletMode())
     is_hotseat_forced_to_show_ = false;
 }
 

ash/shell.cc

@@ -416,6 +416,10 @@ void Shell::OnDictationEnded() {
     observer.OnDictationEnded();
 }
 
+bool Shell::IsInTabletMode() const {
+  return tablet_mode_controller()->InTabletMode();
+}
+
 bool Shell::ShouldSaveDisplaySettings() {
   return !(
       screen_orientation_controller_->ignore_display_configuration_updates() ||

ash/shell.h

@@ -284,7 +284,12 @@ class ASH_EXPORT Shell : public SessionObserver,
   // Called when dictation is ended.
   void OnDictationEnded();
 
-  // Test if TabletModeWindowManager is not enabled, and if
+  // Returns whether the device is currently in tablet mode. If the tablet
+  // mode controller isn't available, we assume the device is not in
+  // tablet mode.
+  bool IsInTabletMode() const;
+
+  // Tests if TabletModeWindowManager is not enabled, and if
   // TabletModeController is not currently setting a display rotation. Or if
   // the |resolution_notification_controller_| is not showing its confirmation
   // dialog. If true then changes to display settings can be saved.
@@ -470,7 +475,7 @@ class ASH_EXPORT Shell : public SessionObserver,
   SystemTrayNotifier* system_tray_notifier() {
     return system_tray_notifier_.get();
   }
-  TabletModeController* tablet_mode_controller() {
+  TabletModeController* tablet_mode_controller() const {
     return tablet_mode_controller_.get();
   }
   ToastManagerImpl* toast_manager() { return toast_manager_.get(); }