Fix appearance of header row separators in table view at fractional

ui/gfx/canvas.h

Index: ui/gfx/canvas.h
diff --git a/ui/gfx/canvas.h b/ui/gfx/canvas.h
index bb2a90e13934f9bf653e9cb85b50dba90b266402..50742de41da41b7d5766ce127c0876cab0e058f6 100644
--- a/ui/gfx/canvas.h
+++ b/ui/gfx/canvas.h
@@ -292,6 +292,10 @@ class GFX_EXPORT Canvas {
                 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)