Enable FastBorderRadius by default on Mac.

Bug: 967076

Change-Id: I9a5fe56098f31d2722fe8b15d1040baa19745a0d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1829940Reviewed-by: Mason Freed <masonfreed@chromium.org>
Commit-Queue: Chris Harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700854}

third_party/blink/common/features.cc

@@ -64,13 +64,7 @@ const base::Feature kDisplayLocking{"DisplayLocking",
 // a mask layer.
 const base::Feature kFastBorderRadius {
   "FastBorderRadius",
-#if defined(OS_MACOSX)
-      // A FastBorderRadiusMac experiment is rolling out separately for that
-      // platform, due to complications with CALayer overlay optimizations.
-      base::FEATURE_DISABLED_BY_DEFAULT
-#else
       base::FEATURE_ENABLED_BY_DEFAULT
-#endif
 };
 
 // Enable LayoutNG.