Unified: Get default focus on detailed view.

In UnifiedSystemTray, detailed view did not get focus when it is
transitioned by keyboard.

TEST=manual
BUG=862504

Change-Id: I9f39359d3fa72be4bff5d42e5a9f98144b1a1bad
Reviewed-on: https://chromium-review.googlesource.com/1132899Reviewed-by: Yoshiki Iguchi <yoshiki@chromium.org>
Commit-Queue: Tetsui Ohkubo <tetsui@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574461}

ash/system/tray/tray_detailed_view.cc

@@ -469,4 +469,9 @@ int TrayDetailedView::GetHeightForWidth(int width) const {
   return height();
 }
 
+void TrayDetailedView::RequestFocus() {
+  if (back_button_)
+    back_button_->RequestFocus();
+}
+
 }  // namespace ash

ash/system/tray/tray_detailed_view.h

@@ -52,6 +52,7 @@ class ASH_EXPORT TrayDetailedView : public views::View,
   // views::View:
   void Layout() override;
   int GetHeightForWidth(int width) const override;
+  void RequestFocus() override;
 
   // Exposes the layout manager of this view to give control to subclasses.
   views::BoxLayout* box_layout() { return box_layout_; }

ash/system/unified/unified_system_tray_controller.cc

@@ -367,8 +367,8 @@ void UnifiedSystemTrayController::ShowDetailedView(
   animation_->Reset(1.0);
   UpdateExpandedAmount();
 
-  unified_view_->SetDetailedView(controller->CreateView());
   unified_view_->SaveFeaturePodFocus();
+  unified_view_->SetDetailedView(controller->CreateView());
   detailed_view_controller_ = std::move(controller);
 }
 

ash/system/unified/unified_system_tray_view.cc

@@ -199,6 +199,8 @@ void UnifiedSystemTrayView::SetDetailedView(views::View* detailed_view) {
   detailed_view_container_->SetPreferredSize(system_tray_size);
   detailed_view->InvalidateLayout();
   Layout();
+
+  detailed_view->RequestFocus();
 }
 
 void UnifiedSystemTrayView::ResetDetailedView() {