[ChromeDriver] Implementing PerfLoggingPrefs for perf log

chrome/test/chromedriver/chrome/devtools_client_impl_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <list>
 #include <string>
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
 #include "base/json/json_reader.h"
@@ skipping 551 matching lines @@
   ASSERT_STREQ("method", event.method.c_str());
   int key;
   ASSERT_TRUE(event.params->GetInteger("key", &key));
   ASSERT_EQ(100, key);
 }
 
 TEST(ParseInspectorMessage, CommandNoErrorOrResult) {
   internal::InspectorMessageType type;
   internal::InspectorEvent event;
   internal::InspectorCommandResponse response;
-  ASSERT_FALSE(internal::ParseInspectorMessage(
+  // As per Chromium issue 392577, DevTools does not necessarily return a
+  // "result" dictionary for every valid response. If neither "error" nor
+  // "result" keys are present, a blank result dictionary should be inferred.
+  ASSERT_TRUE(internal::ParseInspectorMessage(
       "{\"id\":1}", 0, &type, &event, &response));
+  ASSERT_TRUE(response.result->empty());
 }
 
 TEST(ParseInspectorMessage, CommandError) {
   internal::InspectorMessageType type;
   internal::InspectorEvent event;
   internal::InspectorCommandResponse response;
   ASSERT_TRUE(internal::ParseInspectorMessage(
       "{\"id\":1,\"error\":{}}", 0, &type, &event, &response));
   ASSERT_EQ(internal::kCommandResponseMessageType, type);
   ASSERT_EQ(1, response.id);
@@ skipping 555 matching lines @@
   client.AddListener(&listener1);
   client.AddListener(&listener2);
   msgs.push_back("{\"id\": 1, \"result\": {}}");
   msgs.push_back("{\"method\": \"event\", \"params\": {}}");
   base::DictionaryValue params;
   ASSERT_EQ(kOk, client.SendCommand("cmd", params).code());
   ASSERT_EQ(2u, listener2.msgs_.size());
   ASSERT_EQ("cmd", listener2.msgs_.front());
   ASSERT_EQ("event", listener2.msgs_.back());
 }