Revert of Pinch/Zoom Infrastructure & Plumbing CL

cc/animation/scrollbar_animation_controller_thinning.cc

Index: cc/animation/scrollbar_animation_controller_thinning.cc
diff --git a/cc/animation/scrollbar_animation_controller_thinning.cc b/cc/animation/scrollbar_animation_controller_thinning.cc
index 7c10d7a5f9254b1d40c890d40109e9f3b1c85cd5..3de75989d0e47771f64c59f5bf6d4ac1b7a52564 100644
--- a/cc/animation/scrollbar_animation_controller_thinning.cc
+++ b/cc/animation/scrollbar_animation_controller_thinning.cc
@@ -180,22 +180,28 @@
 
 void ScrollbarAnimationControllerThinning::ApplyOpacityAndThumbThicknessScale(
     float opacity, float thumb_thickness_scale) {
-  if (!scroll_layer_->scrollbars())
-    return;
-
-  LayerImpl::ScrollbarSet* scrollbars = scroll_layer_->scrollbars();
-  for (LayerImpl::ScrollbarSet::iterator it = scrollbars->begin();
-       it != scrollbars->end();
-       ++it) {
-    ScrollbarLayerImplBase* scrollbar = *it;
-    if (scrollbar->is_overlay_scrollbar()) {
-      scrollbar->SetOpacity(
-        AdjustScale(opacity, scrollbar->opacity(), opacity_change_));
-    scrollbar->SetThumbThicknessScaleFactor(
-        AdjustScale(thumb_thickness_scale,
-                    scrollbar->thumb_thickness_scale_factor(),
-                    thickness_change_));
-    }
+  ScrollbarLayerImplBase* horizontal_scrollbar =
+      scroll_layer_->horizontal_scrollbar_layer();
+  if (horizontal_scrollbar) {
+    horizontal_scrollbar->SetOpacity(
+        AdjustScale(opacity, horizontal_scrollbar->opacity(), opacity_change_));
+    horizontal_scrollbar->SetThumbThicknessScaleFactor(
+        AdjustScale(
+          thumb_thickness_scale,
+          horizontal_scrollbar->thumb_thickness_scale_factor(),
+          thickness_change_));
+  }
+
+  ScrollbarLayerImplBase* vertical_scrollbar =
+      scroll_layer_->vertical_scrollbar_layer();
+  if (vertical_scrollbar) {
+    vertical_scrollbar->SetOpacity(
+        AdjustScale(opacity, vertical_scrollbar->opacity(), opacity_change_));
+    vertical_scrollbar->SetThumbThicknessScaleFactor(
+        AdjustScale(
+          thumb_thickness_scale,
+          vertical_scrollbar->thumb_thickness_scale_factor(),
+          thickness_change_));
   }
 }