Remove unused base::Thread::thread_handle() getter.

base/threading/thread.h

Index: base/threading/thread.h
diff --git a/base/threading/thread.h b/base/threading/thread.h
index c9a77d7323ecd2477933a67b3b6af4282df3b66c..4be3336697e7337d0f10ad8a70fb89d29ea3e13e 100644
--- a/base/threading/thread.h
+++ b/base/threading/thread.h
@@ -172,9 +172,6 @@ class BASE_EXPORT Thread : PlatformThread::Delegate {
   // Returns the name of this thread (for display in debugger too).
   const std::string& thread_name() const { return name_; }
 
-  // The native thread handle.
-  PlatformThreadHandle thread_handle() { return thread_; }
-
   // Returns the thread ID.  Should not be called before the first Start*()
   // call.  Keeps on returning the same ID even after a Stop() call. The next
   // Start*() call renews the ID.