Deletes base::MessageLoop::set_thread_name().

base/message_loop/message_loop.cc

Index: base/message_loop/message_loop.cc
diff --git a/base/message_loop/message_loop.cc b/base/message_loop/message_loop.cc
index 7038178079fc1619eec2366fc521c335f4fcadab..016ac1901fa678f1652b8caf8c900ac45f35a524 100644
--- a/base/message_loop/message_loop.cc
+++ b/base/message_loop/message_loop.cc
@@ -18,6 +18,7 @@
 #include "base/metrics/statistics_recorder.h"
 #include "base/run_loop.h"
 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
+#include "base/threading/thread_id_name_manager.h"
 #include "base/threading/thread_local.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
@@ -395,7 +396,8 @@ MessageLoop::MessageLoop(Type type, MessagePumpFactoryCallback pump_factory)
       incoming_task_queue_(new internal::IncomingTaskQueue(this)),
       unbound_task_runner_(
           new internal::MessageLoopTaskRunner(incoming_task_queue_)),
-      task_runner_(unbound_task_runner_) {
+      task_runner_(unbound_task_runner_),
+      thread_id_(kInvalidThreadId) {
   // If type is TYPE_CUSTOM non-null pump_factory must be given.
   DCHECK(type_ != TYPE_CUSTOM || !pump_factory_.is_null());
 }
@@ -413,9 +415,15 @@ void MessageLoop::BindToCurrentThread() {
   incoming_task_queue_->StartScheduling();
   unbound_task_runner_->BindToCurrentThread();
   unbound_task_runner_ = nullptr;
+  subtle::Release_Store(&thread_id_, PlatformThread::CurrentId());
   SetThreadTaskRunnerHandle();
 }
 
+std::string MessageLoop::GetThreadName() const {
+  return ThreadIdNameManager::GetInstance()->GetName(
+      subtle::Release_Load(&thread_id_));

[gab, 2016/06/03 15:31:17]

I don't think you need to use an Atomic32. Instead you can initialize
|thread_id_| to |PlatformThread::kInvalidThreadId| and here do:

if (thread_id_ == PlatformThread::kInvalidThreadId) {
  // |thread_id_| should already have been initialized but this thread might not
have received the update yet.
  subtle::MemoryBarrier();
  DCHECK_NE(PlatformThread::kInvalidThreadId, thread_id_);
}
return ThreadIdNameManager::GetInstance()->GetName(thread_id_);

[alokp, 2016/06/03 16:34:56]

Used subtle::MemoryBarrier() in the new patch. I did not add the DCHECK_NE
because I think it is possible that this function is called before
BindToCurrentThread is executed. No?

May be I should add a WARNING that message loop is not bound to any thread yet.
WDYT?

[gab, 2016/06/07 00:30:59]

I think it's reasonable to document in the header that this API is only valid 
when the MessageLoop is running (and BindToCurrentThread is called before the
loop runs [1]). In which case the DCHECK makes sense.

The only place where this is not called from MessageLoop::current() is for
tracing logging when that thread is hung (and thus clearly running).

[1] https://cs.chromium.org/chromium/src/base/threading/thread.cc?rcl=0&l=233

[alokp, 2016/06/10 22:12:59]

Done.

+}
+
 void MessageLoop::SetTaskRunner(
     scoped_refptr<SingleThreadTaskRunner> task_runner) {
   DCHECK_EQ(this, current());
@@ -554,13 +562,12 @@ void MessageLoop::StartHistogrammer() {
 #if !defined(OS_NACL)  // NaCl build has no metrics code.
   if (enable_histogrammer_ && !message_histogram_
       && StatisticsRecorder::IsActive()) {
-    DCHECK(!thread_name_.empty());
+    std::string thread_name = GetThreadName();
+    DCHECK(!thread_name.empty());
     message_histogram_ = LinearHistogram::FactoryGetWithRangeDescription(
-        "MsgLoop:" + thread_name_,
-        kLeastNonZeroMessageId, kMaxMessageId,
+        "MsgLoop:" + thread_name, kLeastNonZeroMessageId, kMaxMessageId,
         kNumberOfDistinctMessagesDisplayed,
-        HistogramBase::kHexRangePrintingFlag,
-        event_descriptions_);
+        HistogramBase::kHexRangePrintingFlag, event_descriptions_);
   }
 #endif
 }