Mirror API for IsAsyncFunction

src/debug/mirrors.js

Index: src/debug/mirrors.js
diff --git a/src/debug/mirrors.js b/src/debug/mirrors.js
index 165e1724492f106896475d3153227c9a1a4bf748..b2510151d38c2caf87fba6c03b1eea623685981d 100644
--- a/src/debug/mirrors.js
+++ b/src/debug/mirrors.js
@@ -1041,6 +1041,11 @@ FunctionMirror.prototype.context = function() {
 };
 
 
+FunctionMirror.prototype.isAsyncFunction = function() {
+  return %FunctionIsAsyncFunction(this.value_);
+}
+
+
 /**
  * Mirror object for unresolved functions.
  * @param {string} value The name for the unresolved function reflected by this