Remove unused methods from rtc::Thread.

These methods are platform specific and give access to member variables
from an unknown thread context (no thread check, no lock).
Since these methods aren't being used, it simplifies a minor refactoring project to simply delete them.

TBR=brandtr@webrtc.org

Bug: webrtc:8596
Change-Id: I85424820d171805dcc3d74317f0e51965402052a
Reviewed-on: https://webrtc-review.googlesource.com/28281
Reviewed-by: Tommi <tommi@webrtc.org>
Commit-Queue: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20983}
diff --git a/rtc_base/thread.h b/rtc_base/thread.h
index bd502eb..3e22c63 100644
--- a/rtc_base/thread.h
+++ b/rtc_base/thread.h
@@ -202,19 +202,6 @@
   // You cannot call Start on non-owned threads.
   bool IsOwned();
 
-#if defined(WEBRTC_WIN)
-  HANDLE GetHandle() const {
-    return thread_;
-  }
-  DWORD GetId() const {
-    return thread_id_;
-  }
-#elif defined(WEBRTC_POSIX)
-  pthread_t GetPThread() {
-    return thread_;
-  }
-#endif
-
   // Expose private method running() for tests.
   //
   // DANGER: this is a terrible public API.  Most callers that might want to