Add ability to retrieve a thread_name given a thread_id.

base/debug/trace_event_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/debug/trace_event_unittest.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/json/json_reader.h"
@@ skipping 60 matching lines @@
   }
 
   void EndTraceAndFlush() {
     TraceLog::GetInstance()->SetDisabled();
     TraceLog::GetInstance()->Flush(
         base::Bind(&TraceEventTestFixture::OnTraceDataCollected,
                    base::Unretained(this)));
   }
 
   virtual void SetUp() OVERRIDE {
-    old_thread_name_ = PlatformThread::GetName();
+    const char* name = PlatformThread::GetName();
+    old_thread_name_ = name ? strdup(name) : NULL;
   }
   virtual void TearDown() OVERRIDE {
     if (TraceLog::GetInstance())
       EXPECT_FALSE(TraceLog::GetInstance()->IsEnabled());
-    PlatformThread::SetName(old_thread_name_ ? old_thread_name_  : "");
+    if (old_thread_name_) {
+      PlatformThread::SetName(old_thread_name_);
+      free(old_thread_name_);
+      old_thread_name_ = NULL;

[jar (doing other things), 2012/12/21 00:17:00]

nit: Using the fact that you can free a NULL pointer with no ill effects, you
could have just added line 89 and 90 to the old code.  I think it would be
easier to read.  Resulting code would read:
PlatformThread::SetName(old_thread_name_ ? old_thread_name_  : "");
free(old_thread_name_);
old_thread_name_ = NULL;

[dsinclair, 2012/12/21 16:28:59]

Done.

That's a lot nicer, didn't realize free(NULL) was a no-op.

+    } else {
+      PlatformThread::SetName("");
+    }
   }
 
-  const char* old_thread_name_;
+  char* old_thread_name_;
   ListValue trace_parsed_;
   base::debug::TraceResultBuffer trace_buffer_;
   base::debug::TraceResultBuffer::SimpleOutput json_output_;
   int event_watch_notification_;
 
  private:
   // We want our singleton torn down after each test.
   ShadowingAtExitManager at_exit_manager_;
   Lock lock_;
 };
@@ skipping 1232 matching lines @@
   Clear();
 
   trace_buffer_.Start();
   trace_buffer_.AddFragment("bla1,bla2,bla3,bla4");
   trace_buffer_.Finish();
   EXPECT_STREQ(json_output_.json_output.c_str(), "[bla1,bla2,bla3,bla4]");
 }
 
 }  // namespace debug
 }  // namespace base