compositor: Tick the UI animations from cc, instead of from timer callbacks.

ash/wm/overview/window_selector_unittest.cc

Index: ash/wm/overview/window_selector_unittest.cc
diff --git a/ash/wm/overview/window_selector_unittest.cc b/ash/wm/overview/window_selector_unittest.cc
index 214104093b949bcebd0b46aca74b267743c4b811..b3c0c05dd0d868f9242754a8c1b7894e4a597b94 100644
--- a/ash/wm/overview/window_selector_unittest.cc
+++ b/ash/wm/overview/window_selector_unittest.cc
@@ -36,6 +36,7 @@
 #include "ui/aura/window.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/compositor/scoped_animation_duration_scale_mode.h"
+#include "ui/compositor/test/layer_animator_collection_test_controller.h"
 #include "ui/gfx/rect_conversions.h"
 #include "ui/gfx/transform.h"
 #include "ui/views/controls/label.h"
@@ -326,6 +327,13 @@ TEST_F(WindowSelectorTest, MinimizedWindowVisibility) {
     EXPECT_FALSE(window1->IsVisible());
     EXPECT_FALSE(window1->layer()->GetTargetVisibility());
   }
+
+  // Toggling overview mode initiates animations on |window1|, as well as other
+  // windows used for the overview mode. Make sure the animations are stopped to
+  // avoid leaking the animators.
+  ui::LayerAnimatorCollectionTestController collection_controller(
+      window1->layer()->GetCompositor()->layer_animator_collection());
+  collection_controller.StopAllAnimators();
 }
 
 // Tests that a bounds change during overview is corrected for.