use SkSurface behind gfx::Canvas

ui/gfx/canvas.cc

Index: ui/gfx/canvas.cc
diff --git a/ui/gfx/canvas.cc b/ui/gfx/canvas.cc
index 9e82c7fc411256174891b9d69c6c7a6ca91b9e78..fd88255bac2c8cbe82d3e0cc33f5510984846c75 100644
--- a/ui/gfx/canvas.cc
+++ b/ui/gfx/canvas.cc
@@ -26,12 +26,21 @@
 
 namespace gfx {
 
+sk_sp<SkSurface> create_surface(int width, int height, bool is_opaque) {

[sadrul, 2017/01/06 05:41:32]

Should be called 'CreateSurface'.

The signature could be "(const gfx::Size& size, bool is_opaque)"

[reed1, 2017/01/06 16:00:37]

Done.

+  // SkSurface cannot be zero-sized, but clients of Canvas sometimes request
+  // that (and then later resize).
+  width = std::max(width, 1);
+  height = std::max(height, 1);
+  SkAlphaType alpha = is_opaque ? kOpaque_SkAlphaType : kPremul_SkAlphaType;
+  SkImageInfo info = SkImageInfo::MakeN32(width, height, alpha);
+  return SkSurface::MakeRaster(info);
+}

[sadrul, 2017/01/06 05:41:32]

This should be in anon namespace.

[reed1, 2017/01/06 16:00:38]

Done.

+
 Canvas::Canvas(const Size& size, float image_scale, bool is_opaque)
     : image_scale_(image_scale) {
   Size pixel_size = ScaleToCeiledSize(size, image_scale);
-  canvas_owner_ = skia::CreatePlatformCanvas(pixel_size.width(),
-                                             pixel_size.height(), is_opaque);
-  canvas_ = canvas_owner_.get();
+  surface_ = create_surface(pixel_size.width(), pixel_size.height(), is_opaque);
+  canvas_ = surface_->getCanvas();
 
 #if !defined(USE_CAIRO)
   // skia::PlatformCanvas instances are initialized to 0 by Cairo, but
@@ -46,8 +55,8 @@ Canvas::Canvas(const Size& size, float image_scale, bool is_opaque)
 
 Canvas::Canvas()
     : image_scale_(1.f),
-      canvas_owner_(skia::CreatePlatformCanvas(0, 0, false)),
-      canvas_(canvas_owner_.get()) {}
+      surface_(create_surface(0, 0, false)),
+      canvas_(surface_->getCanvas()) {}
 
 Canvas::Canvas(SkCanvas* canvas, float image_scale)
     : image_scale_(image_scale), canvas_(canvas) {
@@ -62,9 +71,8 @@ void Canvas::RecreateBackingCanvas(const Size& size,
                                    bool is_opaque) {
   image_scale_ = image_scale;
   Size pixel_size = ScaleToFlooredSize(size, image_scale);
-  canvas_owner_ = skia::CreatePlatformCanvas(pixel_size.width(),

[sadrul, 2017/01/06 05:41:32]

Looks like these are the only uses of skia::CreatePlatformCanvas(). Can that be
removed?

[reed1, 2017/01/06 16:00:38]

Good observation. Florin and I are interleaving CLs as part of the meta-effort
to remove *all* of the platform-canvas infrastructure. I will attempt this
removal in a follow-on CL (partly because it is being called today by
unittests).

-                                             pixel_size.height(), is_opaque);
-  canvas_ = canvas_owner_.get();
+  surface_ = create_surface(pixel_size.width(), pixel_size.height(), is_opaque);
+  canvas_ = surface_->getCanvas();
 
   SkScalar scale_scalar = SkFloatToScalar(image_scale);
   canvas_->scale(scale_scalar, scale_scalar);