Don't set QUIC's write alarm if we are connection flow control blocked.

net/quic/quic_connection.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/quic_connection.h"
 
 #include <string.h>
 #include <sys/types.h>
 #include <algorithm>
 #include <iterator>
@@ skipping 1139 matching lines @@
   }
 
   {  // Limit the scope of the bundler.
     // Set |include_ack| to false in bundler; ack inclusion happens elsewhere.
     ScopedPacketBundler bundler(this, NO_ACK);
     visitor_->OnCanWrite();
   }
 
   // After the visitor writes, it may have caused the socket to become write
   // blocked or the congestion manager to prohibit sending, so check again.
-  if (visitor_->HasPendingWrites() && !resume_writes_alarm_->IsSet() &&
+  if (visitor_->WillingAndAbleToWrite() &&
+      !resume_writes_alarm_->IsSet() &&
       CanWrite(NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA)) {
     // We're not write blocked, but some stream didn't write out all of its
     // bytes. Register for 'immediate' resumption so we'll keep writing after
     // other connections and events have had a chance to use the thread.
     resume_writes_alarm_->Set(clock_->ApproximateNow());
   }
 }
 
 void QuicConnection::WriteIfNotBlocked() {
   if (!writer_->IsWriteBlocked()) {
@@ skipping 791 matching lines @@
   // If we changed the generator's batch state, restore original batch state.
   if (!already_in_batch_mode_) {
     DVLOG(1) << "Leaving Batch Mode.";
     connection_->packet_generator_.FinishBatchOperations();
   }
   DCHECK_EQ(already_in_batch_mode_,
             connection_->packet_generator_.InBatchMode());
 }
 
 }  // namespace net