SkiaRenderer/macOS: Add to about:flags

Bug: 894929
Change-Id: I6e3672659337dd4150de67cb62f5d5dcb27db9de
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2309047
Auto-Submit: ccameron <ccameron@chromium.org>
Commit-Queue: kylechar <kylechar@chromium.org>
Reviewed-by: kylechar <kylechar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790394}

chrome/browser/about_flags.cc

@@ -4861,7 +4861,7 @@ const FeatureEntry kFeatureEntries[] = {
 
     {"enable-skia-renderer", flag_descriptions::kSkiaRendererName,
      flag_descriptions::kSkiaRendererDescription,
-     kOsLinux | kOsWin | kOsAndroid,
+     kOsLinux | kOsWin | kOsAndroid | kOsMac,
      FEATURE_VALUE_TYPE(features::kUseSkiaRenderer)},
 
 #if defined(OS_CHROMEOS)