Change ProcessThread's task type to be the one from TaskQueue.
ProcessThread will eventually be replaced by TaskQueue, so this is the first little step.

BUG=
R=magjed@webrtc.org

Review URL: https://codereview.webrtc.org/2016043003 .

Cr-Commit-Position: refs/heads/master@{#12952}
diff --git a/webrtc/modules/utility/source/process_thread_impl.h b/webrtc/modules/utility/source/process_thread_impl.h
index 330aec9..510ab52 100644
--- a/webrtc/modules/utility/source/process_thread_impl.h
+++ b/webrtc/modules/utility/source/process_thread_impl.h
@@ -33,7 +33,7 @@
   void Stop() override;
 
   void WakeUp(Module* module) override;
-  void PostTask(std::unique_ptr<ProcessTask> task) override;
+  void PostTask(std::unique_ptr<rtc::QueuedTask> task) override;
 
   void RegisterModule(Module* module) override;
   void DeRegisterModule(Module* module) override;
@@ -75,8 +75,7 @@
   std::unique_ptr<rtc::PlatformThread> thread_;
 
   ModuleList modules_;
-  // TODO(tommi): Support delayed tasks.
-  std::queue<ProcessTask*> queue_;
+  std::queue<rtc::QueuedTask*> queue_;
   bool stop_;
   const char* thread_name_;
 };