Adds in-out easing type.

chrome/browser/resources/vr_shell/vr_shell_ui.js

Index: chrome/browser/resources/vr_shell/vr_shell_ui.js
diff --git a/chrome/browser/resources/vr_shell/vr_shell_ui.js b/chrome/browser/resources/vr_shell/vr_shell_ui.js
index 12c5f8cbc26a46dcdc07e8ec3bdcea767e87dd64..a6eedc1c17176e7827b40c024fb323788f347fc6 100644
--- a/chrome/browser/resources/vr_shell/vr_shell_ui.js
+++ b/chrome/browser/resources/vr_shell/vr_shell_ui.js
@@ -109,9 +109,11 @@ var vrShellUi = (function() {
       let anim;
       anim = new api.Animation(this.elementId, ANIM_DURATION);
       anim.setTranslation(0, y, -distance);
+      anim.setEasing(new api.InOutEasing());
       ui.addAnimation(anim);
       anim = new api.Animation(this.elementId, ANIM_DURATION);
       anim.setSize(height * this.SCREEN_RATIO, height);
+      anim.setEasing(new api.InOutEasing());
       ui.addAnimation(anim);
 
       ui.setBackgroundDistance(distance * this.BACKGROUND_DISTANCE_MULTIPLIER);