Use correct theme for the off icon of NightLight, fix tooltip and a11y

ash/system/tiles/tiles_default_view.cc

Index: ash/system/tiles/tiles_default_view.cc
diff --git a/ash/system/tiles/tiles_default_view.cc b/ash/system/tiles/tiles_default_view.cc
index b67d34e8f7c7892197edd54d860fa00eb9eb8a08..12dd62d101475ebf25ef22ed8680b422c0b9e076 100644
--- a/ash/system/tiles/tiles_default_view.cc
+++ b/ash/system/tiles/tiles_default_view.cc
@@ -17,12 +17,14 @@
 #include "ash/system/tray/system_tray_controller.h"
 #include "ash/system/tray/system_tray_item.h"
 #include "ash/system/tray/tray_constants.h"
+#include "ash/system/tray/tray_popup_item_style.h"
 #include "ash/system/tray/tray_popup_utils.h"
 #include "ash/wm/lock_state_controller.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/dbus/session_manager_client.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/gfx/geometry/insets.h"
+#include "ui/gfx/paint_vector_icon.h"
 #include "ui/views/border.h"
 #include "ui/views/controls/button/custom_button.h"
 #include "ui/views/controls/separator.h"
@@ -36,10 +38,25 @@ namespace {
 // not mirrored in this locale.
 const char kHebrewLocale[] = "he";
 
-const gfx::VectorIcon& GetNightLightButtonIcon() {
-  return Shell::Get()->night_light_controller()->GetEnabled()
-             ? kSystemMenuNightLightOnIcon
-             : kSystemMenuNightLightOffIcon;
+// Updates the icon and its style of the NightLight toggle button based on the
+// status of NightLight.
+void UpdateNightLightButtonStyle(SystemMenuButton* night_light_button) {
+  // Use the same icon theme used for inactive items in the tray when
+  // NightLight is not active.
+  SkColor normal_color = TrayPopupItemStyle::GetIconColor(
+      TrayPopupItemStyle::ColorStyle::INACTIVE);
+  const gfx::VectorIcon* icon = &kSystemMenuNightLightOffIcon;
+
+  if (Shell::Get()->night_light_controller()->GetEnabled()) {
+    normal_color = kMenuIconColor;
+    icon = &kSystemMenuNightLightOnIcon;
+  }
+
+  night_light_button->SetImage(views::Button::STATE_NORMAL,
+                               gfx::CreateVectorIcon(*icon, normal_color));
+  night_light_button->SetImage(
+      views::Button::STATE_DISABLED,
+      gfx::CreateVectorIcon(*icon, kMenuIconColorDisabled));

[James Cook, 2017/05/25 02:08:45]

I'm finding this hard to follow. How about creating the 3 icons you need
(apparently normal-state enabled, normal-state disabled, disabled-state
disabled) once TilesDefaultView once and providing 1 or 2 utility functions that
returns the one you need?
 
That might avoid the strange "make it in the off state then fix it" trick below.

[afakhry, 2017/05/25 03:17:54]

Please take a look at the new code. I created a class for the NightLight button
so that I can change its accessibility settings.

I think we might also consider adding another constructor to SystemMenuButton
that doesn't require a VectorIcon.

 }
 
 }  // namespace
@@ -91,9 +108,13 @@ void TilesDefaultView::Init() {
   AddChildView(help_button_);
   AddChildView(TrayPopupUtils::CreateVerticalSeparator());
 
+  // Temporarily create the button with the "Off" icon. Calling
+  // UpdateNightLightButtonStyle() below will set the correct icon and its theme
+  // based on the current status of NightLight.
   night_light_button_ = new SystemMenuButton(
-      this, TrayPopupInkDropStyle::HOST_CENTERED, GetNightLightButtonIcon(),
+      this, TrayPopupInkDropStyle::HOST_CENTERED, kSystemMenuNightLightOffIcon,
       IDS_ASH_STATUS_TRAY_NIGHT_LIGHT);
+  UpdateNightLightButtonStyle(night_light_button_);
   night_light_button_->SetEnabled(can_show_web_ui);
   AddChildView(night_light_button_);
   AddChildView(TrayPopupUtils::CreateVerticalSeparator());
@@ -130,7 +151,7 @@ void TilesDefaultView::ButtonPressed(views::Button* sender,
   } else if (sender == night_light_button_) {
     ShellPort::Get()->RecordUserMetricsAction(UMA_TRAY_NIGHT_LIGHT);
     Shell::Get()->night_light_controller()->Toggle();
-    night_light_button_->SetVectorIcon(GetNightLightButtonIcon());
+    UpdateNightLightButtonStyle(night_light_button_);
   } else if (sender == lock_button_) {
     ShellPort::Get()->RecordUserMetricsAction(UMA_TRAY_LOCK_SCREEN);
     chromeos::DBusThreadManager::Get()