Improve QUIC flow-control commentary and variable-names.

net/quic/core/quic_flow_controller.cc

 // Copyright 2014 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/core/quic_flow_controller.h"
 
 #include <cstdint>
 
 #include "net/quic/core/quic_connection.h"
 #include "net/quic/core/quic_flags.h"
@@ skipping 232 matching lines @@
   // Only update if send window has increased.
   if (new_send_window_offset <= send_window_offset_) {
     return false;
   }
 
   QUIC_DVLOG(1) << ENDPOINT << "UpdateSendWindowOffset for stream " << id_
                 << " with new offset " << new_send_window_offset
                 << " current offset: " << send_window_offset_
                 << " bytes_sent: " << bytes_sent_;
 
-  const bool blocked = IsBlocked();
+  // The flow is now unblocked but could have also been unblocked
+  // before.  Return true iff this update caused a change from blocked
+  // to unblocked.
+  const bool was_previously_blocked = IsBlocked();
   send_window_offset_ = new_send_window_offset;
-  return blocked;
+  return was_previously_blocked;
 }
 
 void QuicFlowController::EnsureWindowAtLeast(QuicByteCount window_size) {
   if (receive_window_size_limit_ >= window_size) {
     return;
   }
 
   QuicStreamOffset available_window = receive_window_offset_ - bytes_consumed_;
   IncreaseWindowSize();
   SendWindowUpdate(available_window);
@@ skipping 17 matching lines @@
   if (receive_window_size_ != receive_window_offset_) {
     QUIC_BUG << "receive_window_size_:" << receive_window_size_
              << " != receive_window_offset:" << receive_window_offset_;
     return;
   }
   receive_window_size_ = size;
   receive_window_offset_ = size;
 }
 
 }  // namespace net