Relax the eplison to check snapping

ui/compositor/dip_util.cc

 // Copyright (c) 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 "ui/compositor/dip_util.h"
 
 #include "base/command_line.h"
 #include "cc/layers/layer.h"
 #include "ui/compositor/compositor.h"
 #include "ui/compositor/compositor_switches.h"
@@ skipping 48 matching lines @@
 
 gfx::Rect ConvertRectToPixel(const Layer* layer,
                              const gfx::Rect& rect_in_dip) {
   return gfx::ConvertRectToPixel(GetDeviceScaleFactor(layer), rect_in_dip);
 }
 
 #if DCHECK_IS_ON()
 namespace {
 
 void CheckSnapped(float snapped_position) {
-  const float kEplison = 0.0001f;
+  const float kEplison = 0.0002f;

[servolk, 2017/03/23 21:49:00]

Nit: fix the typo while you are at it kEplison -> kEpsilon

[servolk, 2017/03/23 21:50:23]

Also, I'm pretty sure 0.0002f is not enough. I have been still getting DCHECKs
when I tried that locally. 0.0005f seems to work fine. But it's still not clear
to me how this value was calculated. Do you mind explaining why you chose
0.0002f?

   float diff = std::abs(snapped_position - gfx::ToRoundedInt(snapped_position));
   DCHECK_LT(diff, kEplison);
 }
 
 }  // namespace
 #endif
 
 void SnapLayerToPhysicalPixelBoundary(ui::Layer* snapped_layer,
                                       ui::Layer* layer_to_snap) {
   DCHECK_NE(snapped_layer, layer_to_snap);
@@ skipping 23 matching lines @@
              layer_to_snap->subpixel_position_offset();
   } else {
     origin = layer_to_snap->position();
   }
   CheckSnapped((layer_offset.x() + origin.x()) * scale_factor);
   CheckSnapped((layer_offset.y() + origin.y()) * scale_factor);
 #endif
 }
 
 }  // namespace ui