Merge Compositor's ScrollbarAnimationControllers into single class

cc/trees/layer_tree_impl.cc

Index: cc/trees/layer_tree_impl.cc
diff --git a/cc/trees/layer_tree_impl.cc b/cc/trees/layer_tree_impl.cc
index ca0f8587a82bc6c479ad0066a2876913db19e478..f58069120922ec79bf6321b8e2fa74ae3089671c 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -24,8 +24,6 @@
 #include "cc/debug/traced_value.h"
 #include "cc/input/page_scale_animation.h"
 #include "cc/input/scrollbar_animation_controller.h"
-#include "cc/input/scrollbar_animation_controller_linear_fade.h"
-#include "cc/input/scrollbar_animation_controller_thinning.h"
 #include "cc/layers/heads_up_display_layer_impl.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/layer_iterator.h"
@@ -1378,17 +1376,19 @@ LayerTreeImpl::CreateScrollbarAnimationController(int scroll_layer_id) {
   base::TimeDelta resize_delay = settings().scrollbar_fade_resize_delay;
   base::TimeDelta fade_duration = settings().scrollbar_fade_duration;
   switch (settings().scrollbar_animator) {
-    case LayerTreeSettings::LINEAR_FADE: {
-      return ScrollbarAnimationControllerLinearFade::Create(
-          scroll_layer_id, layer_tree_host_impl_, delay, resize_delay,
-          fade_duration);
+    case LayerTreeSettings::ANDROID_OVERLAY: {
+      return ScrollbarAnimationController::
+          CreateScrollbarAnimationControllerAndroid(
+              scroll_layer_id, layer_tree_host_impl_, delay, resize_delay,
+              fade_duration);
     }
-    case LayerTreeSettings::THINNING: {
+    case LayerTreeSettings::AURA_OVERLAY: {
       base::TimeDelta thinning_duration =
           settings().scrollbar_thinning_duration;
-      return ScrollbarAnimationControllerThinning::Create(
-          scroll_layer_id, layer_tree_host_impl_, delay, resize_delay,
-          fade_duration, thinning_duration);
+      return ScrollbarAnimationController::
+          CreateScrollbarAnimationControllerAuraOverlay(
+              scroll_layer_id, layer_tree_host_impl_, delay, resize_delay,
+              fade_duration, thinning_duration);
     }
     case LayerTreeSettings::NO_ANIMATOR:
       NOTREACHED();