Add a name to the ProcessThread constructor.

Helps differentiate between different instances when debugging.

Review URL: https://codereview.webrtc.org/1337003003

Cr-Commit-Position: refs/heads/master@{#9927}

webrtc/modules/utility/interface/process_thread.h

@@ -29,7 +29,7 @@ class ProcessThread {
  public:
   virtual ~ProcessThread();
 
-  static rtc::scoped_ptr<ProcessThread> Create();
+  static rtc::scoped_ptr<ProcessThread> Create(const char* thread_name);
 
   // Starts the worker thread.  Must be called from the construction thread.
   virtual void Start() = 0;