Add ability to retrieve a thread_name given a thread_id.

base/debug/trace_event_unittest.cc

Index: base/debug/trace_event_unittest.cc
diff --git a/base/debug/trace_event_unittest.cc b/base/debug/trace_event_unittest.cc
index 445118b6374bd1751df1468d175f7f35db6d8927..357d35c06b6fa5171d7a96609ed8b563f5d7ba8d 100644
--- a/base/debug/trace_event_unittest.cc
+++ b/base/debug/trace_event_unittest.cc
@@ -78,15 +78,22 @@ class TraceEventTestFixture : public testing::Test {
   }
 
   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_;