[inspector] aligned Runtime.evaluate(returnValue:true) result with json

If object contains undefined property then JSON.stringify will skip it,
if array contains undefined as property then JSON.stringify will censor
it to null. [1]

[1] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify

R=alph@chromium.org

Bug: none
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Iafa9d2828d264d89b26675b0e194ad0bfc4621fc
Reviewed-on: https://chromium-review.googlesource.com/834669Reviewed-by: Alexei Filippov <alph@chromium.org>
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50220}

src/inspector/v8-value-utils.cc

@@ -85,6 +85,7 @@ protocol::Response toProtocolValue(v8::Local<v8::Context> context,
       v8::Local<v8::Value> property;
       if (!object->Get(context, name).ToLocal(&property))
         return Response::InternalError();
+      if (property->IsUndefined()) continue;
       std::unique_ptr<protocol::Value> propertyValue;
       Response response =
           toProtocolValue(context, property, maxDepth, &propertyValue);

test/inspector/runtime/runtime-evaluate-null-property-expected.txt

+Tests Runtime.evaluate returns object with undefined property.
+{
+    id : <messageId>
+    result : {
+        result : {
+            type : object
+            value : {
+                b : null
+                c : [
+                    [0] : 1
+                    [1] : null
+                    [2] : null
+                    [3] : 4
+                ]
+            }
+        }
+    }
+}

test/inspector/runtime/runtime-evaluate-null-property.js

+// Copyright 2017 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.
+
+let {session, contextGroup, Protocol} = InspectorTest.start(
+    'Tests Runtime.evaluate returns object with undefined property.');
+
+(async function test() {
+  InspectorTest.logMessage(await Protocol.Runtime.evaluate({
+    expression: '({a:undefined,b:null,c:[1, null, undefined, 4]})',
+    returnByValue: true
+  }));
+  InspectorTest.completeTest();
+})();