[Web Payments] Implement proper focusing in Payment Request

chrome/browser/ui/views/payments/view_stack.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/views/payments/view_stack.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/memory/ptr_util.h"
@@ skipping 31 matching lines @@
   } else {
     view->SetBoundsRect(destination);
     view->Layout();
     AddChildView(view.get());
   }
 
   view->set_owned_by_client();
   // Add the new view to the stack so it can be popped later when navigating
   // back to the previous screen.
   stack_.push_back(std::move(view));
+  RequestFocus();
 }
 
 void ViewStack::Pop() {
   gfx::Rect destination = bounds();
   destination.set_origin(gfx::Point(width(), 0));
 
   slide_out_animator_->AnimateViewTo(
       stack_.back().get(), destination);
 }
 
@@ skipping 26 matching lines @@
   gfx::Rect in_new_destination = bounds();
   in_new_destination.set_origin(gfx::Point(0, 0));
   UpdateAnimatorBounds(slide_in_animator_.get(), in_new_destination);
 
 
   gfx::Rect out_new_destination = bounds();
   out_new_destination.set_origin(gfx::Point(width(), 0));
   UpdateAnimatorBounds(slide_out_animator_.get(), out_new_destination);
 }
 
+void ViewStack::RequestFocus() {
+  // The view can only be focused if it has a widget already. It's possible that
+  // this isn't the case if some views are pushed before the stack is added to a
+  // hierarchy that has a widget.
+  if (top()->GetWidget())
+    top()->RequestFocus();
+}
+
 void ViewStack::UpdateAnimatorBounds(
     views::BoundsAnimator* animator, const gfx::Rect& target) {
   // If an animator is currently animating, figure out which views and update
   // their target bounds.
   if (animator->IsAnimating()) {
     for (auto& view : stack_) {
       if (animator->IsAnimating(view.get())) {
         animator->SetTargetBounds(view.get(), target);
       }
     }
   }
 }
 
 void ViewStack::OnBoundsAnimatorDone(views::BoundsAnimator* animator) {
   // This should only be called from slide_out_animator_ when the views going
   // out are done animating.
   DCHECK_EQ(animator, slide_out_animator_.get());
 
   stack_.pop_back();
   DCHECK(!stack_.empty()) << "State stack should never be empty";
+  RequestFocus();
 }