Merge pull request #949 from rwaldron/755

Fixes for gh-755, per reviews

test/built-ins/Object/prototype/toString/proxy-function.js

+// Copyright (C) 2016 the Apple Inc. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-object.prototype.tostring
+es6id: 19.1.3.6
+description: Proxy of an function is treated as an function
+info: |
+  [...]
+
+  9.5.14 ProxyCreate(target, handler)
+
+  [...]
+  7. If IsCallable(target) is true, then
+    a. Set the [[Call]] internal method of P as specified in 9.5.12.
+  [...]
+
+features: [Proxy]
+---*/
+
+var functionProxy = new Proxy(function() {}, {});
+var functionProxyProxy = new Proxy(functionProxy, {});
+
+assert.sameValue(
+  Object.prototype.toString.call(functionProxy), '[object Function]', 'function proxy'
+);
+assert.sameValue(
+  Object.prototype.toString.call(functionProxyProxy),
+  '[object Function]',
+  'proxy for function proxy'
+);
+
+var arrowProxy = new Proxy(() => {}, {});
+var arrowProxyProxy = new Proxy(arrowProxy, {});
+
+assert.sameValue(
+  Object.prototype.toString.call(arrowProxy), '[object Function]', 'arrow function proxy'
+);
+assert.sameValue(
+  Object.prototype.toString.call(arrowProxyProxy),
+  '[object Function]',
+  'proxy for arrow function proxy'
+);
+
+var generatorProxy = new Proxy(function*() {}, {});
+var generatorProxyProxy = new Proxy(generatorProxy, {});
+
+assert.sameValue(
+  Object.prototype.toString.call(generatorProxy), '[object GeneratorFunction]', 'generator function proxy'
+);
+assert.sameValue(
+  Object.prototype.toString.call(generatorProxyProxy),
+  '[object GeneratorFunction]',
+  'proxy for generator function proxy'
+);
+
+delete generatorProxy.constructor.prototype[Symbol.toStringTag];
+
+assert.sameValue(
+  Object.prototype.toString.call(generatorProxy), '[object Function]', 'generator function proxy without Symbol.toStringTag'
+);
+assert.sameValue(
+  Object.prototype.toString.call(generatorProxyProxy),
+  '[object Function]',
+  'proxy for generator function proxy without Symbol.toStringTag'
+);