Pass widget to ShouldAutoHideTitlebars

This is less likely an issue because I'm no aware of an app that can't
be maximized/snapped in chrome (arc will use different code path)
but this is right thing anyway.

Bug: None
Change-Id: Ia7f49fd99000574b9431218b3be873baed9afdd0
Reviewed-on: https://chromium-review.googlesource.com/987542
Commit-Queue: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547488}

ash/frame/custom_frame_view_ash.cc

@@ -89,9 +89,10 @@ class CustomFrameViewAshWindowStateDelegate : public wm::WindowStateDelegate,
   void OnTabletModeStarted() override {
     if (window_state_->IsFullscreen())
       return;
-
+    views::Widget* widget =
+        views::Widget::GetWidgetForNativeWindow(window_state_->window());
     if (Shell::Get()->tablet_mode_controller()->ShouldAutoHideTitlebars(
-            nullptr)) {
+            widget)) {
       immersive_fullscreen_controller_->SetEnabled(
           ImmersiveFullscreenController::WINDOW_TYPE_OTHER, true);
     }
@@ -132,9 +133,11 @@ class CustomFrameViewAshWindowStateDelegate : public wm::WindowStateDelegate,
   // wm::WindowStateObserver:
   void OnPostWindowStateTypeChange(wm::WindowState* window_state,
                                    mojom::WindowStateType old_type) override {
+    views::Widget* widget =
+        views::Widget::GetWidgetForNativeWindow(window_state->window());
     if (Shell::Get()->tablet_mode_controller() &&
         Shell::Get()->tablet_mode_controller()->ShouldAutoHideTitlebars(
-            nullptr)) {
+            widget)) {
       DCHECK(immersive_fullscreen_controller_);
       if (window_state->IsMinimized() &&
           immersive_fullscreen_controller_->IsEnabled()) {

ash/frame/header_view.cc

@@ -167,7 +167,7 @@ void HeaderView::OnTabletModeStarted() {
   caption_button_container_->UpdateCaptionButtonState(true /*=animate*/);
   parent()->Layout();
   if (Shell::Get()->tablet_mode_controller()->ShouldAutoHideTitlebars(
-          nullptr)) {
+          target_widget_)) {
     target_widget_->non_client_view()->Layout();
   }
 }

ash/wm/tablet_mode/tablet_mode_controller.cc

@@ -223,9 +223,10 @@ void TabletModeController::RemoveObserver(TabletModeObserver* observer) {
 }
 
 bool TabletModeController::ShouldAutoHideTitlebars(views::Widget* widget) {
+  DCHECK(widget);
   const bool tablet_mode = IsTabletModeWindowManagerEnabled();
-  if (!tablet_mode || !widget)
-    return tablet_mode;
+  if (!tablet_mode)
+    return false;
 
   return widget->IsMaximized() ||
          wm::GetWindowState(widget->GetNativeWindow())->IsSnapped();

ash/wm/tablet_mode/tablet_mode_controller.h

@@ -103,9 +103,7 @@ class ASH_EXPORT TabletModeController
   void AddObserver(TabletModeObserver* observer);
   void RemoveObserver(TabletModeObserver* observer);
 
-  // Checks if we should auto hide title bars in tablet mode. If |widget| is not
-  // null this also checks if the window associated with |widget| is in an auto
-  // hide state.
+  // Checks if we should auto hide title bars for the |widget| in tablet mode.
   bool ShouldAutoHideTitlebars(views::Widget* widget);
 
   // Flushes the mojo message pipe to chrome.