Previews should exclude a property if its name is a symbol

test/inspector/runtime/evaluate-with-generate-preview.js

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 print("Tests that Runtime.evaluate will generate correct previews.");
 
 InspectorTest.addScript(
 `
+var sym = Symbol(123);
+
 Object.prototype[0] = 'default-first';
-var obj = {p1: {a:1}, p2: {b:'foo'}};
+var obj = {p1: {a:1}, p2: {b:'foo'}, p3: sym};
 Object.defineProperties(obj, {
-  p3: {
+  p4: {
     get() { return 2 }
   },
-  p4: {
+  p5: {
     set(x) { return x }
   },
-  p5: {
+  p6: {
     get() { return 2 },
     set(x) { return x }
   }
 });
+obj[sym] = 'baz';
 
 Array.prototype[0] = 'default-first';
-var arr = [,, 1, [2]];
+var arr = [,, 1, [2], sym];
 Object.defineProperties(arr, {
-  4: {
+  5: {
     get() { return 2 }
   },
-  5: {
+  6: {
     set(x) { return x }
   },
-  6: {
+  7: {
     get() { return 2 },
     set(x) { return x }
   }
 });
+arr[sym] = 'baz';
 `);
 
 InspectorTest.runTestSuite([
   function testObjectPropertiesPreview(next)
   {
     Protocol.Runtime.evaluate({ "expression": "obj", "generatePreview": true })
         .then(result => InspectorTest.logMessage(result.result.result.preview))
         .then(next);
   },
 
   function testArrayPropertiesPreview(next)
   {
     Protocol.Runtime.evaluate({ "expression": "arr", "generatePreview": true })
         .then(result => InspectorTest.logMessage(result.result.result.preview))
         .then(next);
   }
 ]);