Make CanvasPainter raster directly to an SkBitmap

ui/compositor/paint_context.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_PAINT_CONTEXT_H_
 #define UI_COMPOSITOR_PAINT_CONTEXT_H_
 
 #include <memory>
 
 #include "base/logging.h"
@@ skipping 47 matching lines @@
   void Visited(void* visited) const {
     if (!root_visited_)
       root_visited_ = visited;
   }
   void* RootVisited() const { return root_visited_; }
   const gfx::Vector2d& PaintOffset() const { return offset_; }
 #endif
 
   const gfx::Rect& InvalidationForTesting() const { return invalidation_; }
 
+  float device_scale_factor() const { return device_scale_factor_; }

[danakj, 2017/02/14 21:37:26]

It doesn't look like you need to add this if u store the raster scale. My
thought is that this API is intentionally left bare so it is very clear to go
thru a *Recorder to do anything, and PaintRecorder has a gfx::Canvas with a
scale on it.

+
  private:
   // The Recorder classes need access to the internal canvas and friends, but we
   // don't want to expose them on this class so that people must go through the
   // recorders to access them.
   friend class ClipRecorder;
   friend class CompositingRecorder;
   friend class PaintRecorder;
   friend class TransformRecorder;
   // The Cache class also needs to access the DisplayItemList to append its
   // cache contents.
@@ skipping 30 matching lines @@
   // recorder is active.
   mutable bool inside_paint_recorder_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(PaintContext);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_PAINT_CONTEXT_H_