Fix comment.

This CL lands part of internal change 201519764.  The rest of that
change has been merged in https://crrev.com/c/1121700 (reviewed at
https://crrev.com/c/1121285).

Bug: 488484
Change-Id: I78b225c43af626eb7c6e3054b85e44018387b8cb
Reviewed-on: https://chromium-review.googlesource.com/1146664
Commit-Queue: Yang Song <yasong@chromium.org>
Reviewed-by: Yang Song <yasong@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577927}

net/third_party/spdy/core/priority_write_scheduler.h

@@ -250,8 +250,7 @@ class PriorityWriteScheduler : public WriteScheduler<StreamIdType> {
   // Returns the number of ready streams.
   size_t NumReadyStreams() const override { return num_ready_streams_; }
 
-  // This function is used for debugging and test only. Returns true if a stream
-  // is ready.
+  // Returns true if a stream is ready.
   bool IsStreamReady(StreamIdType stream_id) const {
     auto it = stream_infos_.find(stream_id);
     if (it == stream_infos_.end()) {