Only allow static strings as ProcessThread names.

Review URL: https://codereview.webrtc.org/1336293002

Cr-Commit-Position: refs/heads/master@{#9932}
diff --git a/webrtc/modules/utility/source/process_thread_impl.cc b/webrtc/modules/utility/source/process_thread_impl.cc
index eab0d9a..51b7494 100644
--- a/webrtc/modules/utility/source/process_thread_impl.cc
+++ b/webrtc/modules/utility/source/process_thread_impl.cc
@@ -77,7 +77,7 @@
   }
 
   thread_ = ThreadWrapper::CreateThread(&ProcessThreadImpl::Run, this,
-                                        thread_name_.c_str());
+                                        thread_name_);
   CHECK(thread_->Start());
 }