Hide scrollbars when their dimensions are not scrollable.

cc/layers/layer_impl.h

 // Copyright 2011 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.
 
 #ifndef CC_LAYERS_LAYER_IMPL_H_
 #define CC_LAYERS_LAYER_IMPL_H_
 
 #include <set>
 #include <string>
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/values.h"
 #include "cc/animation/animation_delegate.h"
 #include "cc/animation/layer_animation_controller.h"
 #include "cc/animation/layer_animation_value_observer.h"
 #include "cc/animation/layer_animation_value_provider.h"
 #include "cc/base/cc_export.h"
 #include "cc/base/region.h"
 #include "cc/base/scoped_ptr_vector.h"
 #include "cc/input/input_handler.h"
+#include "cc/input/scrollbar.h"
 #include "cc/layers/draw_properties.h"
 #include "cc/layers/layer_lists.h"
 #include "cc/layers/layer_position_constraint.h"
 #include "cc/layers/render_surface_impl.h"
 #include "cc/output/filter_operations.h"
 #include "cc/quads/shared_quad_state.h"
 #include "cc/resources/resource_provider.h"
 #include "skia/ext/refptr.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "third_party/skia/include/core/SkImageFilter.h"
@@ skipping 371 matching lines @@
   void SetScrollClipLayer(int scroll_clip_layer_id);
   LayerImpl* scroll_clip_layer() const { return scroll_clip_layer_; }
   bool scrollable() const { return !!scroll_clip_layer_; }
 
   void set_user_scrollable_horizontal(bool scrollable) {
     user_scrollable_horizontal_ = scrollable;
   }
   void set_user_scrollable_vertical(bool scrollable) {
     user_scrollable_vertical_ = scrollable;
   }
+  bool user_scrollable(ScrollbarOrientation orientation) const;
 
   void ApplySentScrollDeltasFromAbortedCommit();
   void ApplyScrollDeltasSinceBeginMainFrame();
 
   void SetShouldScrollOnMainThread(bool should_scroll_on_main_thread) {
     should_scroll_on_main_thread_ = should_scroll_on_main_thread;
   }
   bool should_scroll_on_main_thread() const {
     return should_scroll_on_main_thread_;
   }
@@ skipping 284 matching lines @@
   DrawProperties<LayerImpl> draw_properties_;
 
   scoped_refptr<base::debug::ConvertableToTraceFormat> debug_info_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_