Reland "Makes wallpaper dim in tablet mode, without relying on app_list_shield"

This is a reland of 0b107635

Includes changes to fix MSAN issues

Bug: 898712, 899158

Original change's description:
> Makes wallpaper dim in tablet mode, without relying on app_list_shield
>
> Bug: 898712
> Change-Id: I96ba08fec3f7df8547d753ff4d31366345be0ac8
> Reviewed-on: https://chromium-review.googlesource.com/c/1298507
> Reviewed-by: Weidong Guo <weidongg@chromium.org>
> Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
> Commit-Queue: Kevin Strohbehn <ginko@google.com>
> Cr-Commit-Position: refs/heads/master@{#602938}

Bug: 898712
Change-Id: Ief534b6dc58b5d36b3f96952141a51312c50a79f
Reviewed-on: https://chromium-review.googlesource.com/c/1303233
Commit-Queue: Kevin Strohbehn <ginko@google.com>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603605}

ash/app_list/app_list_presenter_delegate_unittest.cc

@@ -1188,9 +1188,9 @@ TEST_F(AppListPresenterDelegateHomeLauncherTest, BackgroundOpacity) {
       GetAppListView()->GetAppListBackgroundShieldForTest()->layer();
   EXPECT_EQ(0.7f, background_layer->opacity());
 
-  // Turn on tablet mode. The background sheild opacity should be 10%.
+  // Turn on tablet mode. The background shield should be transparent.
   EnableTabletMode(true);
-  EXPECT_EQ(0.4f, background_layer->opacity());
+  EXPECT_EQ(0.f, background_layer->opacity());
 }
 
 // Tests that the background blur is disabled for the app list.

ash/app_list/views/app_list_view.cc

@@ -89,9 +89,6 @@ constexpr float kAppListAnimationDurationTestMs = 0;
 constexpr float kAppListAnimationDurationMs = 200;
 constexpr float kAppListAnimationDurationFromFullscreenMs = 250;
 
-// The app list opacity when the tablet mode is enabled.
-constexpr float kAppListOpacityInTabletMode = 0.4;
-
 // The background corner radius in peeking and fullscreen state.
 constexpr int kAppListBackgroundRadius = 28;
 
@@ -1120,8 +1117,7 @@ void AppListView::OnTabletModeChanged(bool started) {
       parent_window->AddChild(window);
 
     // Update background opacity.
-    app_list_background_shield_->layer()->SetOpacity(
-        kAppListOpacityInTabletMode);
+    app_list_background_shield_->layer()->SetOpacity(0.f);
 
     // Update background blur.
     if (is_background_blur_enabled_)

ash/wallpaper/wallpaper_view.cc

@@ -31,6 +31,10 @@
 namespace ash {
 namespace {
 
+// The value used for alpha to apply a dark filter to the wallpaper in tablet
+// mode. A higher number up to 255 results in a darker wallpaper.
+constexpr int kWallpaperDimnessInTabletMode = 102;
+
 // A view that controls the child view's layer so that the layer always has the
 // same size as the display's original, un-scaled size in DIP. The layer is then
 // transformed to fit to the virtual screen size when laid-out. This is to avoid
@@ -85,6 +89,10 @@ SkColor GetWallpaperDarkenColor() {
   return SkColorSetA(darken_color, login_constants::kTranslucentAlpha);
 }
 
+SkColor GetWallpaperDarkenColorForTabletMode() {
+  return SkColorSetA(GetWallpaperDarkenColor(), kWallpaperDimnessInTabletMode);
+}
+
 }  // namespace
 
 // This event handler receives events in the pre-target phase and takes care of
@@ -131,12 +139,30 @@ WallpaperView::WallpaperView()
     : pre_dispatch_handler_(new PreEventDispatchHandler()) {
   set_context_menu_controller(this);
   AddPreTargetHandler(pre_dispatch_handler_.get());
+  tablet_mode_observer_.Add(Shell::Get()->tablet_mode_controller());
+  is_tablet_mode_ = Shell::Get()
+                        ->tablet_mode_controller()
+                        ->IsTabletModeWindowManagerEnabled();
 }
 
 WallpaperView::~WallpaperView() {
   RemovePreTargetHandler(pre_dispatch_handler_.get());
 }
 
+void WallpaperView::OnTabletModeStarted() {
+  is_tablet_mode_ = true;
+  SchedulePaint();
+}
+
+void WallpaperView::OnTabletModeEnded() {
+  is_tablet_mode_ = false;
+  SchedulePaint();
+}
+
+void WallpaperView::OnTabletControllerDestroyed() {
+  tablet_mode_observer_.RemoveAll();
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // WallpaperView, views::View overrides:
 
@@ -160,6 +186,9 @@ void WallpaperView::OnPaint(gfx::Canvas* canvas) {
   if (controller->ShouldApplyDimming()) {
     flags.setColorFilter(SkColorFilter::MakeModeFilter(
         GetWallpaperDarkenColor(), SkBlendMode::kDarken));
+  } else if (is_tablet_mode_) {
+    flags.setColorFilter(SkColorFilter::MakeModeFilter(
+        GetWallpaperDarkenColorForTabletMode(), SkBlendMode::kDarken));
   }
 
   switch (layout) {

ash/wallpaper/wallpaper_view.h

@@ -7,6 +7,9 @@
 
 #include <memory>
 
+#include "ash/wm/tablet_mode/tablet_mode_controller.h"
+#include "ash/wm/tablet_mode/tablet_mode_observer.h"
+#include "base/scoped_observer.h"
 #include "ui/views/context_menu_controller.h"
 #include "ui/views/view.h"
 
@@ -18,7 +21,9 @@ namespace ash {
 
 class PreEventDispatchHandler;
 
-class WallpaperView : public views::View, public views::ContextMenuController {
+class WallpaperView : public views::View,
+                      public views::ContextMenuController,
+                      TabletModeObserver {
  public:
   WallpaperView();
   ~WallpaperView() override;
@@ -30,10 +35,20 @@ class WallpaperView : public views::View, public views::ContextMenuController {
   void OnPaint(gfx::Canvas* canvas) override;
   bool OnMousePressed(const ui::MouseEvent& event) override;
 
+  // Overridden from TabletModeObserver:
+  void OnTabletModeStarted() override;
+  void OnTabletModeEnded() override;
+  void OnTabletControllerDestroyed() override;
+
   // Overridden from views::ContextMenuController:
   void ShowContextMenuForView(views::View* source,
                               const gfx::Point& point,
                               ui::MenuSourceType source_type) override;
+
+  ScopedObserver<TabletModeController, TabletModeObserver>
+      tablet_mode_observer_{this};
+  bool is_tablet_mode_ = false;
+
   std::unique_ptr<PreEventDispatchHandler> pre_dispatch_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(WallpaperView);

ash/wm/overview/window_grid.cc

@@ -33,6 +33,7 @@
 #include "ash/wm/overview/window_selector_delegate.h"
 #include "ash/wm/overview/window_selector_item.h"
 #include "ash/wm/splitview/split_view_drag_indicators.h"
+#include "ash/wm/tablet_mode/tablet_mode_controller.h"
 #include "ash/wm/tablet_mode/tablet_mode_window_state.h"
 #include "ash/wm/window_state.h"
 #include "ash/wm/window_util.h"
@@ -206,7 +207,12 @@ class WindowGrid::ShieldView : public views::View {
     background_view_ = new views::View();
     background_view_->SetPaintToLayer(ui::LAYER_SOLID_COLOR);
     background_view_->layer()->SetColor(kShieldBaseColor);
-    background_view_->layer()->SetOpacity(kShieldOpacity);
+    background_view_->layer()->SetOpacity(
+        !Shell::Get()
+                ->tablet_mode_controller()
+                ->IsTabletModeWindowManagerEnabled()
+            ? kShieldOpacity
+            : 0.f);
 
     label_ = new views::Label(
         l10n_util::GetStringUTF16(IDS_ASH_OVERVIEW_NO_RECENT_ITEMS),

ash/wm/overview/window_grid.h

@@ -58,9 +58,9 @@ class ASH_EXPORT WindowGrid : public aura::WindowObserver,
              const gfx::Rect& bounds_in_screen);
   ~WindowGrid() override;
 
-  // The opacity of the shield widget that is used to darden the background of
+  // The opacity of the shield widget that is used to darken the background of
   // the grid.
-  static constexpr float kShieldOpacity = 0.6f;
+  static constexpr float kShieldOpacity = 0.4f;
 
   // Returns the shield color that is used to darken the background of the grid.
   static SkColor GetShieldColor();

ash/wm/tablet_mode/tablet_mode_controller.cc

@@ -166,6 +166,9 @@ TabletModeController::~TabletModeController() {
   chromeos::DBusThreadManager::Get()->GetPowerManagerClient()->RemoveObserver(
       this);
 
+  for (auto& observer : tablet_mode_observers_)
+    observer.OnTabletControllerDestroyed();
+
   TabletMode::SetCallback(TabletMode::TabletModeCallback());
 }
 

ash/wm/tablet_mode/tablet_mode_observer.h

@@ -29,8 +29,12 @@ class ASH_EXPORT TabletModeObserver {
   // connected.
   virtual void OnTabletModeEventsBlockingChanged() {}
 
+  // Called when the tablet mode controller is destroyed, to help manage issues
+  // with observers being destroyed after controllers.
+  virtual void OnTabletControllerDestroyed() {}
+
  protected:
-  virtual ~TabletModeObserver() {}
+  virtual ~TabletModeObserver() = default;
 };
 
 }  // namespace ash