[WebPayments] Implement state transitions in desktop WebPayments dialog.

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

+// 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.
+
+#ifndef CHROME_BROWSER_UI_VIEWS_PAYMENTS_VIEW_STACK_H_
+#define CHROME_BROWSER_UI_VIEWS_PAYMENTS_VIEW_STACK_H_
+
+#include "ui/views/view.h"
+#include "ui/views/animation/bounds_animator.h"
+#include "ui/views/animation/bounds_animator_observer.h"
+
+// This view represents a stack of views that slide in over one another from
+// left to right. It manages the animation and lifetime of views that are
+// pushed and popped on it. To use this class, add it to a view hierarchy, and
+// call Push/Pop to animate views in and out.
+class ViewStack : public views::BoundsAnimatorObserver,
+                  public views::View {
+ public:
+  ViewStack();
+  ~ViewStack() override;
+
+  // Adds a view to the stack and starts animating it in from the right. This
+  // takes ownership of the view and calls set_owned_by_client() on it.
+  // If |animate| is false, the view will simply be added to the hierarchy
+  // without the sliding animation.
+  void Push(std::unique_ptr<views::View> state, bool animate);
+
+  // Removes a view from the stack, animates it out of view, and makes sure
+  // it's properly deleted after the animation.
+  void Pop();
+
+  // views::View:
+  // The children of this view must not be able to process events when the views
+  // are being animated so this returns false when an animation is in progress.
+  bool CanProcessEventsWithinSubtree() const override;
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(
+      ViewStackTest, TestPopStateRemovesChildViewAndCleansUpState);
+
+  FRIEND_TEST_ALL_PREFIXES(ViewStackTest, TestDeletingViewCleansUpState);
+
+  // Returns the top state of the stack, used in tests.
+  views::View* top() { return stack_.top().get(); }
+
+  // views::BoundsAnimatorObserver:
+  void OnBoundsAnimatorProgressed(views::BoundsAnimator* animator) override {}
+  void OnBoundsAnimatorDone(views::BoundsAnimator* animator) override;
+
+  std::stack<std::unique_ptr<views::View>> stack_;
+
+  std::unique_ptr<views::BoundsAnimator> slide_in_animator_;
+  std::unique_ptr<views::BoundsAnimator> slide_out_animator_;
+
+  DISALLOW_COPY_AND_ASSIGN(ViewStack);
+};
+
+#endif  // CHROME_BROWSER_UI_VIEWS_PAYMENTS_VIEW_STACK_H_