use skia cgimage->bitmap routine

skia/ext/skia_utils_mac.mm

Index: skia/ext/skia_utils_mac.mm
diff --git a/skia/ext/skia_utils_mac.mm b/skia/ext/skia_utils_mac.mm
index 57fb7076ba219c4b5ccefb292200c69b5d644638..bc3039794cb6efc7e039e33508c0fb884529a53d 100644
--- a/skia/ext/skia_utils_mac.mm
+++ b/skia/ext/skia_utils_mac.mm
@@ -184,31 +184,10 @@ NSColor* SkColorToSRGBNSColor(SkColor color) {
 }
 
 SkBitmap CGImageToSkBitmap(CGImageRef image) {
-  if (!image)
-    return SkBitmap();
-
-  int width = CGImageGetWidth(image);
-  int height = CGImageGetHeight(image);
-
-  std::unique_ptr<SkCanvas> canvas(skia::CreatePlatformCanvas(
-      nullptr, width, height, false, RETURN_NULL_ON_FAILURE));
-  ScopedPlatformPaint p(canvas.get());
-  CGContextRef context = p.GetNativeDrawingContext();
-
-  // We need to invert the y-axis of the canvas so that Core Graphics drawing
-  // happens right-side up. Skia has an upper-left origin and CG has a lower-
-  // left one.
-  CGContextScaleCTM(context, 1.0, -1.0);
-  CGContextTranslateCTM(context, 0, -height);
-
-  // We want to copy transparent pixels from |image|, instead of blending it
-  // onto uninitialized pixels.
-  CGContextSetBlendMode(context, kCGBlendModeCopy);
-
-  CGRect rect = CGRectMake(0, 0, width, height);
-  CGContextDrawImage(context, rect, image);
-
-  return skia::ReadPixels(canvas.get());
+  SkBitmap bm;

[dcheng, 2016/12/21 22:37:22]

Nit: bitmap

[reed1, 2016/12/22 13:42:53]

Done.

+  if (image && SkCreateBitmapFromCGImage(&bm, image))
+    return bm;
+  return SkBitmap();

[dcheng, 2016/12/21 22:37:22]

This is technically unnecessary, since SkCreateBitmapFromCGImage() states that
it leaves the original SkBitmap untouched. TBH, I'm uncertain what the value of
the return value here is; I could only find one caller, and they don't even
check the return value.

[reed1, 2016/12/22 13:42:53]

It is a convenience if the caller wants to know if it failed, without having to
also check the out-parameter afterwards.

 }
 
 SkBitmap NSImageToSkBitmapWithColorSpace(