Downgrade QUIC flow control violation ERROR log to DLOG(INFO).

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 "base/strings/stringprintf.h"
 #include "net/quic/core/quic_bug_tracker.h"
 #include "net/quic/core/quic_connection.h"
 #include "net/quic/core/quic_flags.h"
@@ skipping 73 matching lines @@
         ConnectionCloseBehavior::SEND_CONNECTION_CLOSE_PACKET);
     return;
   }
 
   bytes_sent_ += bytes_sent;
   DVLOG(1) << ENDPOINT << "Stream " << id_ << " sent: " << bytes_sent_;
 }
 
 bool QuicFlowController::FlowControlViolation() {
   if (highest_received_byte_offset_ > receive_window_offset_) {
-    LOG(ERROR) << ENDPOINT << "Flow control violation on stream " << id_
+    DLOG(INFO) << ENDPOINT << "Flow control violation on stream " << id_
                << ", receive window offset: " << receive_window_offset_
                << ", highest received byte offset: "
                << highest_received_byte_offset_;
     return true;
   }
   return false;
 }
 
 void QuicFlowController::MaybeIncreaseMaxWindowSize() {
   // Core of receive window auto tuning.  This method should be called before a
@@ skipping 140 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