Support offset-TypedArray in futex API

src/futex-emulation.cc

Index: src/futex-emulation.cc
diff --git a/src/futex-emulation.cc b/src/futex-emulation.cc
index b0e514e8af2a11c8094f2438fa651ed4172fb142..991e4c371169156d7c596197b3895d80071f9ccc 100644
--- a/src/futex-emulation.cc
+++ b/src/futex-emulation.cc
@@ -262,7 +262,8 @@ Object* FutexEmulation::NumWaitersForTesting(Isolate* isolate,
   int waiters = 0;
   FutexWaitListNode* node = wait_list_.Pointer()->head_;
   while (node) {
-    if (backing_store == node->backing_store_ && addr == node->wait_addr_) {
+    if (backing_store == node->backing_store_ && addr == node->wait_addr_ &&
+        node->waiting_) {
       waiters++;
     }