Uses an open thread handle as the ThreadJoinId on Windows.

runtime/bin/thread_android.cc

Index: runtime/bin/thread_android.cc
diff --git a/runtime/bin/thread_android.cc b/runtime/bin/thread_android.cc
index 4f5c5479d7354170936823d33ff8e89a32e30b4a..ce27ea322691b0680f9cd50c7c82511ca3370b1b 100644
--- a/runtime/bin/thread_android.cc
+++ b/runtime/bin/thread_android.cc
@@ -155,11 +155,6 @@ ThreadId Thread::GetCurrentThreadId() {
 }
 
 
-bool Thread::Join(ThreadId id) {
-  return false;
-}
-
-
 intptr_t Thread::ThreadIdToIntPtr(ThreadId id) {
   ASSERT(sizeof(id) == sizeof(intptr_t));
   return static_cast<intptr_t>(id);