Use animated vector icon for app menu notification animation.

ui/views/controls/animated_icon_view.h

+// Copyright 2017 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 UI_VIEWS_CONTROLS_ANIMATED_ICON_VIEW_H_
+#define UI_VIEWS_CONTROLS_ANIMATED_ICON_VIEW_H_
+
+#include "base/macros.h"
+#include "base/time/time.h"
+#include "ui/compositor/compositor_animation_observer.h"
+#include "ui/gfx/vector_icon_types.h"
+#include "ui/views/controls/image_view.h"
+
+namespace views {
+
+// This class hosts a vector icon that defines transitions. It can be in the
+// start steady state, the end steady state, or transitioning in between.
+class AnimatedIconView : public views::ImageView,
+                         public ui::CompositorAnimationObserver {
+ public:
+  enum State {
+    START,
+    END,

[sadrul, 2017/05/23 18:01:14]

Does it not need a TRANSITION state?

[Evan Stade, 2017/05/23 23:38:42]

no, this enum just describes the static state. When transitioning (IsAnimating()
is true), |state_| defines the target.

+  };
+
+  explicit AnimatedIconView(const gfx::VectorIcon& icon);
+  ~AnimatedIconView() override;
+
+  void set_color(SkColor color) { color_ = color; }
+
+  // Animates to the end or start state.
+  void Animate(State target);
+
+  // Jumps to the end or start state.
+  void SetState(State state);
+
+  // views::ImageView
+  void OnPaint(gfx::Canvas* canvas) override;
+
+  // ui::CompositorAnimationObserver
+  void OnAnimationStep(base::TimeTicks timestamp) override;
+  void OnCompositingShuttingDown(ui::Compositor* compositor) override;
+
+ private:
+  bool IsAnimating();
+
+  void UpdateStaticImage();
+
+  const gfx::VectorIcon& icon_;
+  SkColor color_;

[sadrul, 2017/05/23 18:01:14]

It's curious that we don't have this for ImageView itself. How is the color set
for those?

[Evan Stade, 2017/05/23 23:38:42]

ImageView doesn't know about VectorIcon, it only deals in ImageSkia.

+
+  // Tracks the last time Animate() was called.
+  base::TimeTicks start_time_;
+
+  // The amount of time that must elapse until all transitions are done, i.e.
+  // the length of the animation.
+  const base::TimeDelta duration_;
+
+  // The current state, or when transitioning the goal state.
+  State state_ = START;
+
+  DISALLOW_COPY_AND_ASSIGN(AnimatedIconView);
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_CONTROLS_ANIMATED_ICON_VIEW_H_