Scrollbar ThumbLength is not updated when window size is changed.

cc/layers/painted_scrollbar_layer.cc

 // Copyright 2013 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_scrollbar_layer.h"
 
 #include "base/auto_reset.h"
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
 #include "cc/layers/painted_scrollbar_layer_impl.h"
@@ skipping 171 matching lines @@
         gfx::Size(scrollbar_->ThumbThickness(), scrollbar_->ThumbLength());
   }
   return gfx::Rect(thumb_size);
 }
 
 void PaintedScrollbarLayer::UpdateThumbAndTrackGeometry() {
   UpdateProperty(scrollbar_->TrackRect(), &track_rect_);
   UpdateProperty(scrollbar_->Location(), &location_);
   UpdateProperty(scrollbar_->IsOverlay(), &is_overlay_);
   UpdateProperty(scrollbar_->HasThumb(), &has_thumb_);
-  if (has_thumb_) {
-    UpdateProperty(scrollbar_->ThumbThickness(), &thumb_thickness_);
-    UpdateProperty(scrollbar_->ThumbLength(), &thumb_length_);
-  }
+  UpdateProperty(scrollbar_->ThumbThickness(), &thumb_thickness_);
+  UpdateProperty(scrollbar_->ThumbLength(), &thumb_length_);
 }
 
 bool PaintedScrollbarLayer::Update(ResourceUpdateQueue* queue,
                                    const OcclusionTracker<Layer>* occlusion) {
   UpdateThumbAndTrackGeometry();
 
   gfx::Rect track_layer_rect = gfx::Rect(location_, bounds());
   gfx::Rect scaled_track_rect = ScrollbarLayerRectToContentRect(
       track_layer_rect);
 
   if (track_rect_.IsEmpty() || scaled_track_rect.IsEmpty())

[danakj, 2014/09/03 17:20:51]

This function never destroys the thumb_resource_ or the track_resource_. Maybe
it should be dropping those resources rather than holding onto their memory when
the track_rect_ is empty, and/or the thumb is missing/empty? Maybe you can
follow up on this with another CL?

[MuVen, 2014/09/03 18:08:47]

Sure. Will work on this.

     return false;
 
   {
     base::AutoReset<bool> ignore_set_needs_commit(&ignore_set_needs_commit_,
                                                   true);
     ContentsScalingLayer::Update(queue, occlusion);
   }
 
   if (update_rect_.IsEmpty() && track_resource_)
     return false;
@@ skipping 46 matching lines @@
 
   scrollbar_->PaintPart(&skcanvas, part, layer_rect);
   // Make sure that the pixels are no longer mutable to unavoid unnecessary
   // allocation and copying.
   skbitmap.setImmutable();
 
   return UIResourceBitmap(skbitmap);
 }
 
 }  // namespace cc