<rdar://problem/20402026> Remove scope entry/exit log entries

Don't emit scope entry/exit logging code in instrumentation for
playgrounds if -playground-high-performance option is passed.

Swift SVN r27046

include/swift/Frontend/FrontendOptions.h

@@ -196,6 +196,10 @@ public:
   /// Indicates whether the playground transformation should be applied.
   bool PlaygroundTransform = false;
 
+  /// Indicates whether the playground transformation should omit
+  /// instrumentation that has a high runtime performance impact.
+  bool PlaygroundHighPerformance = false;
+
   /// Indicates whether standard help should be shown.
   bool PrintHelp = false;