[ash-md] Remove the number of animators used for the Shelf animations.

ui/gfx/animation/slide_animation.cc

Index: ui/gfx/animation/slide_animation.cc
diff --git a/ui/gfx/animation/slide_animation.cc b/ui/gfx/animation/slide_animation.cc
index 780e8ec8b0fa70593b13042edc5b228484e067d2..e410935cbd520fb09313e5c7b882b1de5b2bdab7 100644
--- a/ui/gfx/animation/slide_animation.cc
+++ b/ui/gfx/animation/slide_animation.cc
@@ -6,6 +6,9 @@
 
 #include <math.h>
 
+#include "base/auto_reset.h"
+#include "ui/gfx/animation/animation_delegate.h"
+
 namespace gfx {
 
 // How long animations should take by default.
@@ -46,6 +49,8 @@ void SlideAnimation::Show() {
   // Make sure we actually have something to do.
   if (slide_duration_ == 0) {
     AnimateToState(1.0);  // Skip to the end of the animation.
+    if (delegate())
+      delegate()->AnimationProgressed(this);

[James Cook, 2017/02/08 00:31:28]

Do you know offhand if any of Chrome's other users of SlideAnimation depend on
duration 0?

[bruthig, 2017/02/10 18:49:10]

I did a quick audit and it appears there might be 3 cases where a slide duration
of 0 may be used:
- ImmersiveFullscreenController
- ScrollAnimator
- OmniboxResultView::OnBoundsChanged()

Oddly enough there is a BoundsAnimatorDisabler in shelf_view.cc that uses a
duration of 1.  Seems like a work around for some undesirable behaviour when the
duration is 0.

IMO the SlideAnimation doesn't support this case well and it should probably be
fixed or removed.

     return;
   } else if (value_current_ == value_end_)  {
     return;
@@ -56,6 +61,11 @@ void SlideAnimation::Show() {
   Start();
 }
 
+void SlideAnimation::ShowImmediately() {
+  base::AutoReset<int> auto_reset_duration(&slide_duration_, 0);
+  Show();
+}
+
 void SlideAnimation::Hide() {
   // If we're already hiding (or hidden), we have nothing to do.
   if (!showing_)
@@ -67,7 +77,9 @@ void SlideAnimation::Hide() {
 
   // Make sure we actually have something to do.
   if (slide_duration_ == 0) {
-    AnimateToState(0.0);  // Skip to the end of the animation.
+    AnimateToState(1.0);  // Skip to the end of the animation.
+    if (delegate())
+      delegate()->AnimationProgressed(this);
     return;
   } else if (value_current_ == value_end_) {
     return;
@@ -78,6 +90,11 @@ void SlideAnimation::Hide() {
   Start();
 }
 
+void SlideAnimation::HideImmediately() {
+  base::AutoReset<int> auto_reset_duration(&slide_duration_, 0);
+  Hide();
+}
+
 void SlideAnimation::SetSlideDuration(int duration) {
   slide_duration_ = duration;
 }