Implements core logic for Pixel Canvas

ui/compositor/canvas_painter.h

Index: ui/compositor/canvas_painter.h
diff --git a/ui/compositor/canvas_painter.h b/ui/compositor/canvas_painter.h
index 1db206f36b04de853da9dbcc592fff89392f4782..da44d7bb16654f76ee9f2ec57aeb4a8906f5b61e 100644
--- a/ui/compositor/canvas_painter.h
+++ b/ui/compositor/canvas_painter.h
@@ -29,7 +29,8 @@ class COMPOSITOR_EXPORT CanvasPainter {
   CanvasPainter(SkBitmap* output,
                 const gfx::Size& paint_size,
                 float raster_scale,
-                SkColor clear_color);
+                SkColor clear_color,
+                bool is_pixel_canvas);

[sky, 2017/07/26 22:12:11]

Document what is_pixel_canvas means. Also, I'm wondering if is_pixel_canvas
should have a default value to avoid having to supply false everywhere.

[sky, 2017/07/26 23:16:41]

Dana says she prefers no default args, which I'm ok with. So, ignore this
comment. Sorry for the churn.

[malaykeshav, 2017/07/28 01:24:37]

Do we need to document this here? It is only required to initialize the
ui::PaintContext where it is documented.

[sky, 2017/07/28 16:02:10]

It wasn't obvious to me what this means on first look, so yes, it needs some
documentation. We don't want to duplicate documentation though, so you can say
see PaintContext for details on |is_pixel_canvas|.

   ~CanvasPainter();
 
   const PaintContext& context() const { return context_; }