Vertical GlowEffect shown on about:blank page in low end devices

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/json/json_reader.h"
 #include "base/strings/stringprintf.h"
 #include "cc/animation/animation_registrar.h"
@@ skipping 1175 matching lines @@
   }
   // TODO(wjmaclean) Once we move to a model where the two-viewport model is
   // turned on in all builds, remove the next two lines. For now however, the
   // page scale layer may coincide with the clip layer, and so this is
   // necessary.
   if (page_scale_layer == scroll_clip_layer_)
     scale_factor *= layer_tree_impl()->total_page_scale_factor();
 
   scaled_scroll_bounds.SetSize(scale_factor * scaled_scroll_bounds.width(),
                                scale_factor * scaled_scroll_bounds.height());
+  scaled_scroll_bounds = gfx::ToFlooredSize(scaled_scroll_bounds);
 
   gfx::Vector2dF max_offset(
       scaled_scroll_bounds.width() - scroll_clip_layer_->bounds().width(),
       scaled_scroll_bounds.height() - scroll_clip_layer_->bounds().height());
   // We need the final scroll offset to be in CSS coords.
   max_offset.Scale(1 / scale_factor);
   max_offset.SetToMax(gfx::Vector2dF());
   return gfx::ToFlooredVector2d(max_offset);

[aelias_OOO_until_Jul13, 2014/04/16 22:25:43]

There's already a floor here that's supposed to fix this, seems it's not working
properly.  I think we should have at most one floor in this function.  Would it
work to move the floor before max_offset.Scale(1 / scale_factor); ?

 }
 
 gfx::Vector2dF LayerImpl::ClampScrollToMaxScrollOffset() {
   gfx::Vector2dF max_offset = MaxScrollOffset();
   gfx::Vector2dF old_offset = TotalScrollOffset();
   gfx::Vector2dF clamped_offset = old_offset;
 
   clamped_offset.SetToMin(max_offset);
   clamped_offset.SetToMax(gfx::Vector2d());
   gfx::Vector2dF delta = clamped_offset - old_offset;
@@ skipping 286 matching lines @@
 scoped_ptr<base::Value> LayerImpl::AsValue() const {
   scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue());
   AsValueInto(state.get());
   return state.PassAs<base::Value>();
 }
 
 void LayerImpl::RunMicroBenchmark(MicroBenchmarkImpl* benchmark) {
   benchmark->RunOnLayer(this);
 }
 }  // namespace cc