Don't Unblock twice when flushing the compiler job queue

BUG=none
R=yangguo@chromium.org

Change-Id: I683c10eae10f60fb7239f3714df0a12a9d19a43b
Reviewed-on: https://chromium-review.googlesource.com/480071Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Jochen Eisinger <jochen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44674}

src/compiler-dispatcher/optimizing-compile-dispatcher.cc

@@ -135,8 +135,8 @@ void OptimizingCompileDispatcher::FlushOutputQueue(bool restore_function_code) {
 }
 
 void OptimizingCompileDispatcher::Flush(BlockingBehavior blocking_behavior) {
-  if (FLAG_block_concurrent_recompilation) Unblock();
   if (blocking_behavior == BlockingBehavior::kDontBlock) {
+    if (FLAG_block_concurrent_recompilation) Unblock();
     base::LockGuard<base::Mutex> access_input_queue_(&input_queue_mutex_);
     while (input_queue_length_ > 0) {
       CompilationJob* job = input_queue_[InputQueueIndex(0)];