Deleted OS_WIN and all Windows specific files from base.

base/threading/thread.h

Index: base/threading/thread.h
diff --git a/base/threading/thread.h b/base/threading/thread.h
index 0bd5d12922f1395bf3a93f99af6207fe27bdd2a4..b7b94d8939ce661cf76298fff8d56dc80374793b 100644
--- a/base/threading/thread.h
+++ b/base/threading/thread.h
@@ -79,18 +79,6 @@ class BASE_EXPORT Thread : PlatformThread::Delegate {
   // before it is destructed.
   ~Thread() override;
 
-#if defined(OS_WIN)
-  // Causes the thread to initialize COM.  This must be called before calling
-  // Start() or StartWithOptions().  If |use_mta| is false, the thread is also
-  // started with a TYPE_UI message loop.  It is an error to call
-  // init_com_with_mta(false) and then StartWithOptions() with any message loop
-  // type other than TYPE_UI.
-  void init_com_with_mta(bool use_mta) {
-    DCHECK(!start_event_);
-    com_status_ = use_mta ? MTA : STA;
-  }
-#endif
-
   // Starts the thread.  Returns true if the thread was successfully started;
   // otherwise, returns false.  Upon successful return, the message_loop()
   // getter will return non-null.
@@ -209,22 +197,9 @@ class BASE_EXPORT Thread : PlatformThread::Delegate {
   }
 
  private:
-#if defined(OS_WIN)
-  enum ComStatus {
-    NONE,
-    STA,
-    MTA,
-  };
-#endif
-
   // PlatformThread::Delegate methods:
   void ThreadMain() override;
 
-#if defined(OS_WIN)
-  // Whether this thread needs to initialize COM, and if so, in what mode.
-  ComStatus com_status_;
-#endif
-
   // If true, we're in the middle of stopping, and shouldn't access
   // |message_loop_|. It may non-NULL and invalid.
   bool stopping_;