Hide pinch viewport scrollbars when near minimum scale.

cc/layers/layer_impl.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layers/layer_impl.h"
 
 #include "base/debug/trace_event.h"
 #include "base/debug/trace_event_argument.h"
 #include "base/json/json_reader.h"
 #include "base/strings/stringprintf.h"
@@ skipping 1313 matching lines @@
     scrollbar_needs_animation |=
         scrollbar_layer->SetVisibleToTotalLengthRatio(visible_ratio);
   }
   if (scrollbar_needs_animation) {
     layer_tree_impl()->set_needs_update_draw_properties();
     // TODO(wjmaclean) The scrollbar animator for the pinch-zoom scrollbars
     // should activate for every scroll on the main frame, not just the
     // scrolls that move the pinch virtual viewport (i.e. trigger from
     // either inner or outer viewport).
     if (scrollbar_animation_controller_) {
-      // When both non-overlay and overlay scrollbars are both present, don't
-      // animate the overlay scrollbars when page scale factor is at the min.
-      // Non-overlay scrollbars also shouldn't trigger animations.
-      bool is_animatable_scrollbar =
-          scrollbar_layer->is_overlay_scrollbar() &&
-          ((layer_tree_impl()->current_page_scale_factor() >
-            layer_tree_impl()->min_page_scale_factor()) ||
-           !layer_tree_impl()->settings().use_pinch_zoom_scrollbars);
-      if (is_animatable_scrollbar)
+      // Non-overlay scrollbars shouldn't trigger animations.
+      if (scrollbar_layer->is_overlay_scrollbar())
         scrollbar_animation_controller_->DidScrollUpdate(on_resize);
     }
   }
 }
 
 void LayerImpl::DidBecomeActive() {
   if (layer_tree_impl_->settings().scrollbar_animator ==
       LayerTreeSettings::NoAnimator) {
     return;
   }
@@ skipping 242 matching lines @@
   SetNeedsPushProperties();
   layer_tree_impl()->set_needs_update_draw_properties();
   if (should_have_render_surface) {
     render_surface_ = make_scoped_ptr(new RenderSurfaceImpl(this));
     return;
   }
   render_surface_.reset();
 }
 
 }  // namespace cc