Add some changes to TraceAnalyzer to improve analysis

base/test/trace_event_analyzer_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 "base/test/trace_event_analyzer.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/bind.h"
@@ skipping 590 matching lines @@
       TraceAnalyzer::Create(output_.json_output));
   ASSERT_TRUE(analyzer.get());
   analyzer->AssociateAsyncBeginEndEvents();
 
   TraceEventVector found;
   analyzer->FindEvents(Query::MatchAsyncBeginWithNext(), &found);
   ASSERT_EQ(3u, found.size());
 
   EXPECT_STRCASEEQ("0xb", found[0]->id.c_str());
   EXPECT_EQ(TRACE_EVENT_PHASE_ASYNC_STEP_PAST, found[0]->other_event->phase);
+  EXPECT_EQ(found[0], found[0]->other_event->prev_event);
   EXPECT_TRUE(found[0]->other_event->other_event);
   EXPECT_EQ(TRACE_EVENT_PHASE_ASYNC_END,
             found[0]->other_event->other_event->phase);
+  EXPECT_EQ(found[0]->other_event,
+            found[0]->other_event->other_event->prev_event);
 
   EXPECT_STRCASEEQ("0xc", found[1]->id.c_str());
   EXPECT_EQ(TRACE_EVENT_PHASE_ASYNC_STEP_INTO, found[1]->other_event->phase);
+  EXPECT_EQ(found[1], found[1]->other_event->prev_event);
   EXPECT_TRUE(found[1]->other_event->other_event);
   EXPECT_EQ(TRACE_EVENT_PHASE_ASYNC_STEP_INTO,
             found[1]->other_event->other_event->phase);
+  EXPECT_EQ(found[1]->other_event,
+            found[1]->other_event->other_event->prev_event);
   double arg_actual = 0;
   EXPECT_TRUE(found[1]->other_event->other_event->GetArgAsNumber(
                   "a", &arg_actual));
   EXPECT_EQ(1.0, arg_actual);
   EXPECT_TRUE(found[1]->other_event->other_event->other_event);
   EXPECT_EQ(TRACE_EVENT_PHASE_ASYNC_END,
             found[1]->other_event->other_event->other_event->phase);
 
   EXPECT_STRCASEEQ("0xa", found[2]->id.c_str());
   EXPECT_EQ(TRACE_EVENT_PHASE_ASYNC_STEP_INTO, found[2]->other_event->phase);
@@ skipping 316 matching lines @@
   std::unique_ptr<base::Value> arg;
   events[0]->GetArgAsValue("arg", &arg);
   base::DictionaryValue* arg_dict;
   EXPECT_TRUE(arg->GetAsDictionary(&arg_dict));
   std::string property;
   EXPECT_TRUE(arg_dict->GetString("property", &property));
   EXPECT_EQ("value", property);
 }
 
 }  // namespace trace_analyzer