Fix appearance of header row separators in table view at fractional

ui/gfx/canvas.h

 // 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.
 
 #ifndef UI_GFX_CANVAS_H_
 #define UI_GFX_CANVAS_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 274 matching lines @@
   // Draws a line with the given |flags| parameters.
   // DEPRECATED in favor of the RectF version below.
   // TODO(funkysidd): Remove this (http://crbug.com/553726)
   void DrawLine(const Point& p1, const Point& p2, const cc::PaintFlags& flags);
 
   // Draws a line with the given |flags| parameters.
   void DrawLine(const PointF& p1,
                 const PointF& p2,
                 const cc::PaintFlags& flags);
 
+  // Draws a line that's a single DIP. At fractional scale factors, this is
+  // floored to the nearest integral number of pixels.
+  void DrawSharpLine(const PointF& p1, const PointF& p2, SkColor color);

[Peter Kasting, 2017/02/15 00:43:59]

Nit: Is "Sharp" the best name for this?  "DrawIntegralPxLine" maybe?  I can't
think of anything non-awkward, but when I read "Sharp" I assumed it meant a
hairline, if I knew what it meant at all.

[Evan Stade, 2017/02/15 16:54:46]

well, naming is hard. I like Sharp better than IntegralPxLine (which sounds to
me like 1px?) but I think in both cases if I found it in the code I'd need to
resort to looking up the docs to figure out what was going on and why it was
necessary.

I agree it's possible we might want/be able to replace DrawLine with this at
which point we can just rename to DrawLine.

+
   // Draws a circle with the given |flags| parameters.
   // DEPRECATED in favor of the RectF version below.
   // TODO(funkysidd): Remove this (http://crbug.com/553726)
   void DrawCircle(const Point& center_point,
                   int radius,
                   const cc::PaintFlags& flags);
 
   // Draws a circle with the given |flags| parameters.
   void DrawCircle(const PointF& center_point,
                   float radius,
@@ skipping 203 matching lines @@
   // but surface_ will be null.
   sk_sp<cc::PaintSurface> surface_;
   cc::PaintCanvas* canvas_;
 
   DISALLOW_COPY_AND_ASSIGN(Canvas);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_CANVAS_H_