Implements core logic for Pixel Canvas

ui/compositor/canvas_painter.h

 // Copyright 2015 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_COMPOSITOR_CANVAS_PAINTER_H_
 #define UI_COMPOSITOR_CANVAS_PAINTER_H_
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "ui/compositor/compositor_export.h"
@@ skipping 11 matching lines @@
 // CanvasPainter, the context() can be used to do painting using the normal
 // composited paint paths.  When the painter is destroyed, any painting done
 // with the context() will be rastered into the provided output bitmap.
 //
 // TODO(enne): rename this class to be PaintContextRasterizer or some such.
 class COMPOSITOR_EXPORT CanvasPainter {
  public:
   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_; }
 
  private:
   SkBitmap* const output_;
   const gfx::Size paint_size_;
   const float raster_scale_;
   const SkColor clear_color_;
   scoped_refptr<cc::DisplayItemList> list_;
   PaintContext context_;
 
   DISALLOW_COPY_AND_ASSIGN(CanvasPainter);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_CANVAS_PAINTER_H_