Migrate to OS_MAC and OS_APPLE in skia

Bug: 1105907
Change-Id: Iced94df0bfda68ba8f04792a88dd136395621ab0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2324900Reviewed-by: Stephen White <senorblanco@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#792843}

skia/ext/platform_canvas_unittest.cc

@@ -75,7 +75,7 @@ bool VerifyRect(const SkCanvas& canvas,
   return true;
 }
 
-#if !defined(USE_AURA) && !defined(OS_MACOSX)
+#if !defined(USE_AURA) && !defined(OS_MAC)
 // Return true if canvas has something that passes for a rounded-corner
 // rectangle. Basically, we're just checking to make sure that the pixels in the
 // middle are of rect_color and pixels in the corners are of canvas_color.