[WebPayments] Implement state transitions in desktop WebPayments dialog.

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 "ui/views/layout/fill_layout.h"
+
+ViewStack::ViewStack()
+    : slide_in_animator_(base::MakeUnique<views::BoundsAnimator>(this)),
+      slide_out_animator_(base::MakeUnique<views::BoundsAnimator>(this)) {
+  SetLayoutManager(new views::FillLayout());
+
+  slide_out_animator_->AddObserver(this);
+}
+
+ViewStack::~ViewStack() {}
+
+void ViewStack::Push(std::unique_ptr<views::View> view, bool animate) {
+  gfx::Rect destination = bounds();
+  destination.set_origin(gfx::Point(0, 0));
+  if (animate) {
+    // First add the new view out of bounds since it'll slide in from right to
+    // left.
+    view->SetBounds(width(), 0, width(), height());
+    view->Layout();
+
+    AddChildView(view.get());
+
+    // Animate the new view to be right on top of this one.
+    slide_in_animator_->AnimateViewTo(view.get(), destination);
+  } 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(std::move(view));
+}
+
+void ViewStack::Pop() {
+  gfx::Rect destination = bounds();
+  destination.set_origin(gfx::Point(width(), 0));
+
+  slide_out_animator_->AnimateViewTo(
+      stack_.top().get(), destination);
+}
+
+bool ViewStack::CanProcessEventsWithinSubtree() const {
+  return !slide_in_animator_->IsAnimating() &&
+         !slide_out_animator_->IsAnimating();
+}
+
+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();
+  DCHECK(!stack_.empty()) << "State stack should never be empty";
+}