Repaint overlay scrollbar if resource is disposed.

cc/layers/painted_overlay_scrollbar_layer.cc

 // Copyright 2016 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/painted_overlay_scrollbar_layer.h"
 
 #include <algorithm>
 
 #include "base/auto_reset.h"
 #include "cc/base/math_util.h"
@@ skipping 120 matching lines @@
   updated |= UpdateProperty(scrollbar_->TrackRect(), &track_rect_);
   updated |= UpdateProperty(scrollbar_->Location(), &location_);
   updated |= UpdateProperty(scrollbar_->ThumbThickness(), &thumb_thickness_);
   updated |= UpdateProperty(scrollbar_->ThumbLength(), &thumb_length_);
   updated |= PaintThumbIfNeeded();
 
   return updated;
 }
 
 bool PaintedOverlayScrollbarLayer::PaintThumbIfNeeded() {
-  if (!scrollbar_->NeedsPaintPart(THUMB))
+  if (!scrollbar_->NeedsPaintPart(THUMB) && thumb_resource_)
     return false;
 
   gfx::Rect paint_rect = OriginThumbRectForPainting();
   aperture_ = scrollbar_->NinePatchThumbAperture();
 
   DCHECK(!paint_rect.size().IsEmpty());
   DCHECK(paint_rect.origin().IsOrigin());
 
   SkBitmap skbitmap;
   skbitmap.allocN32Pixels(paint_rect.width(), paint_rect.height());
@@ skipping 13 matching lines @@
 
   thumb_resource_ = ScopedUIResource::Create(
       layer_tree_host()->GetUIResourceManager(), UIResourceBitmap(skbitmap));
 
   SetNeedsPushProperties();
 
   return true;
 }
 
 }  // namespace cc