Revert of Change ProcessThread's task type to be the one from TaskQueue.

webrtc/modules/utility/include/process_thread.h

Index: webrtc/modules/utility/include/process_thread.h
diff --git a/webrtc/modules/utility/include/process_thread.h b/webrtc/modules/utility/include/process_thread.h
index 8524a5188eb2d9446d5b1c40a08549ef488061b1..f6913ea3167481eef084579aaf38be0c54088aeb 100644
--- a/webrtc/modules/utility/include/process_thread.h
+++ b/webrtc/modules/utility/include/process_thread.h
@@ -15,23 +15,17 @@
 
 #include "webrtc/typedefs.h"
 
-#if defined(WEBRTC_WIN)
-// Due to a bug in the std::unique_ptr implementation that ships with MSVS,
-// we need the full definition of QueuedTask, on Windows.
-#include "webrtc/base/task_queue.h"
-#else
-namespace rtc {
-class QueuedTask;
-}
-#endif
-
 namespace webrtc {
 class Module;
 
-// TODO(tommi): ProcessThread probably doesn't need to be a virtual
-// interface.  There exists one override besides ProcessThreadImpl,
-// MockProcessThread, but when looking at how it is used, it seems
-// a nullptr might suffice (or simply an actual ProcessThread instance).
+class ProcessTask {
+ public:
+  ProcessTask() {}
+  virtual ~ProcessTask() {}
+
+  virtual void Run() = 0;
+};
+
 class ProcessThread {
  public:
   virtual ~ProcessThread();
@@ -57,7 +51,7 @@
   // construction thread of the ProcessThread instance, if the task did not
   // get a chance to run (e.g. posting the task while shutting down or when
   // the thread never runs).
-  virtual void PostTask(std::unique_ptr<rtc::QueuedTask> task) = 0;
+  virtual void PostTask(std::unique_ptr<ProcessTask> task) = 0;
 
   // Adds a module that will start to receive callbacks on the worker thread.
   // Can be called from any thread.