Revert "CrOS Shelf: Set right margin on status area based on tablet mode"

This reverts commit a1297fc3.

Reason for revert: Broke test with hotseat feature enabled.

Original change's description:
> CrOS Shelf: Set right margin on status area based on tablet mode
> 
> With this change, the padding between the edge of the screen and the
> status area widget no longer has anything to do with the hotseat
> state. This edge padding will now only ever have two possible values,
> one value in tablet mode and another value in clamshell mode.
> 
> Bug: 1035716
> Change-Id: I70f8ffe99ddf8e44482a3c9772f72dcf7adb9885
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1977025
> Reviewed-by: Tetsui Ohkubo <tetsui@chromium.org>
> Reviewed-by: Manu Cornet <manucornet@chromium.org>
> Commit-Queue: Matthew Mourgos <mmourgos@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#727486}

TBR=tetsui@chromium.org,manucornet@chromium.org,mmourgos@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1035716
Change-Id: If730127fc7471d9a063fb45530c81b99b2abd035
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1983328Reviewed-by: Matthew Mourgos <mmourgos@chromium.org>
Commit-Queue: Matthew Mourgos <mmourgos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#727623}

ash/system/status_area_widget_delegate.cc

@@ -7,11 +7,11 @@
 #include "ash/focus_cycler.h"
 #include "ash/root_window_controller.h"
 #include "ash/shelf/shelf.h"
+#include "ash/shelf/shelf_layout_manager.h"
 #include "ash/shelf/shelf_widget.h"
 #include "ash/shell.h"
 #include "ash/system/status_area_widget.h"
 #include "ash/system/tray/tray_constants.h"
-#include "ash/wm/tablet_mode/tablet_mode_controller.h"
 #include "chromeos/constants/chromeos_switches.h"
 #include "ui/compositor/layer.h"
 #include "ui/compositor/scoped_layer_animation_settings.h"
@@ -86,6 +86,7 @@ StatusAreaWidgetDelegate::StatusAreaWidgetDelegate(Shelf* shelf)
   set_owned_by_client();  // Deleted by DeleteDelegate().
 
   ShelfConfig::Get()->AddObserver(this);
+  shelf_->shelf_layout_manager()->AddObserver(this);
 
   // Allow the launcher to surrender the focus to another window upon
   // navigation completion by the user.
@@ -96,6 +97,7 @@ StatusAreaWidgetDelegate::StatusAreaWidgetDelegate(Shelf* shelf)
 
 StatusAreaWidgetDelegate::~StatusAreaWidgetDelegate() {
   ShelfConfig::Get()->RemoveObserver(this);
+  shelf_->shelf_layout_manager()->RemoveObserver(this);
 }
 
 void StatusAreaWidgetDelegate::SetFocusCyclerForTesting(
@@ -178,6 +180,21 @@ void StatusAreaWidgetDelegate::OnShelfConfigUpdated() {
   UpdateLayout();
 }
 
+void StatusAreaWidgetDelegate::OnHotseatStateChanged(HotseatState old_state,
+                                                     HotseatState new_state) {
+  // Update the border of the last visible child so it has the right
+  // padding depending of the state of the shelf (See
+  // https://crbug.com/1025270). Don't layout as it will cause the whole
+  // transition to snap instead of animate (See https://crbug.com/1032770).
+  auto it = std::find_if(children().crbegin(), children().crend(),
+                         [](const View* v) { return v->GetVisible(); });
+  if (it == children().crend())
+    return;
+
+  View* last_visible_child = *it;
+  SetBorderOnChild(last_visible_child, /*is_child_on_edge=*/true);
+}
+
 void StatusAreaWidgetDelegate::UpdateLayout() {
   // Use a grid layout so that the trays can be centered in each cell, and
   // so that the widget gets laid out correctly when tray sizes change.
@@ -257,13 +274,11 @@ void StatusAreaWidgetDelegate::SetBorderOnChild(views::View* child,
   // items also takes care of padding at the edge of the shelf.
   int right_edge = kPaddingBetweenWidgetsNewUi;
 
-  const bool tablet_mode =
-      Shell::Get()->tablet_mode_controller() &&
-      Shell::Get()->tablet_mode_controller()->InTabletMode();
-
-  if (is_child_on_edge && !tablet_mode &&
-      chromeos::switches::ShouldShowShelfHotseat()) {
-    right_edge = kPaddingBetweenWidgetAndRightScreenEdge;
+  if (is_child_on_edge && chromeos::switches::ShouldShowShelfHotseat()) {
+    right_edge =
+        shelf_->shelf_layout_manager()->hotseat_state() == HotseatState::kShown
+            ? kPaddingBetweenWidgetAndRightScreenEdge
+            : 0;
   }
 
   // Swap edges if alignment is not horizontal (bottom-to-top).

ash/system/status_area_widget_delegate.h

@@ -8,6 +8,7 @@
 #include "ash/ash_export.h"
 #include "ash/public/cpp/shelf_config.h"
 #include "ash/public/cpp/shelf_types.h"
+#include "ash/shelf/shelf_layout_manager_observer.h"
 #include "ash/system/status_area_widget.h"
 #include "base/macros.h"
 #include "ui/gfx/image/image_skia.h"
@@ -21,7 +22,8 @@ class Shelf;
 // The View for the status area widget.
 class ASH_EXPORT StatusAreaWidgetDelegate : public views::AccessiblePaneView,
                                             public views::WidgetDelegate,
-                                            public ShelfConfig::Observer {
+                                            public ShelfConfig::Observer,
+                                            public ShelfLayoutManagerObserver {
  public:
   explicit StatusAreaWidgetDelegate(Shelf* shelf);
   ~StatusAreaWidgetDelegate() override;
@@ -59,6 +61,10 @@ class ASH_EXPORT StatusAreaWidgetDelegate : public views::AccessiblePaneView,
   // Overridden from ShelfConfig::Observer:
   void OnShelfConfigUpdated() override;
 
+  // ShelfLayoutManagerObserver:
+  void OnHotseatStateChanged(HotseatState old_state,
+                             HotseatState new_state) override;
+
   void set_default_last_focusable_child(bool default_last_focusable_child) {
     default_last_focusable_child_ = default_last_focusable_child;
   }