ash: Make the buttons in the tray-popup headers accessible from keyboard.

ash/system/tray/tray_views.cc

Index: ash/system/tray/tray_views.cc
diff --git a/ash/system/tray/tray_views.cc b/ash/system/tray/tray_views.cc
index e27814016483dc7d01477bded2d9445318bc496e..99efb4e6971bbe001f90ce83dddbe930b5765730 100644
--- a/ash/system/tray/tray_views.cc
+++ b/ash/system/tray/tray_views.cc
@@ -292,6 +292,7 @@ TrayPopupHeaderButton::TrayPopupHeaderButton(views::ButtonListener* listener,
                     views::ImageButton::ALIGN_MIDDLE);
   set_background(views::Background::CreateSolidBackground(
       ash::kHeaderBackgroundColor));
+  set_focusable(true);
 }
 
 TrayPopupHeaderButton::~TrayPopupHeaderButton() {}
@@ -305,6 +306,13 @@ void TrayPopupHeaderButton::OnPaintBorder(gfx::Canvas* canvas) {
   canvas->FillRect(gfx::Rect(0, 0, 1, height()), ash::kBorderDarkColor);
 }
 
+void TrayPopupHeaderButton::OnPaintFocusBorder(gfx::Canvas* canvas) {
+  if (HasFocus() && (focusable() || IsAccessibilityFocusable())) {
+    canvas->DrawRect(gfx::Rect(2, 1, width() - 4, height() - 3),
+                     kFocusBorderColor);
+  }
+}
+
 void TrayPopupHeaderButton::StateChanged() {
   set_background(views::Background::CreateSolidBackground(
       IsHotTracked() ? ash::kHeaderHoverBackgroundColor :