Fix a QUIC flow control bug where a stream is flow control blocked when

the config is negotiated and it never gets to write again.

Merge internal change: 77003200

R=rch@chromium.org
BUG=423024

Review URL: https://codereview.chromium.org/639713007

Cr-Commit-Position: refs/heads/master@{#299339}

net/quic/quic_flow_controller.cc

@@ -163,10 +163,12 @@ bool QuicFlowController::UpdateSendWindowOffset(uint64 new_send_window_offset) {
 
   DVLOG(1) << ENDPOINT << "UpdateSendWindowOffset for stream " << id_
            << " with new offset " << new_send_window_offset
-           << " , current offset: " << send_window_offset_;
+           << " current offset: " << send_window_offset_
+           << " bytes_sent: " << bytes_sent_;
 
+  const bool blocked = IsBlocked();
   send_window_offset_ = new_send_window_offset;
-  return true;
+  return blocked;
 }
 
 void QuicFlowController::Disable() {

net/quic/quic_flow_controller.h

@@ -47,8 +47,7 @@ class NET_EXPORT_PRIVATE QuicFlowController {
   void AddBytesSent(uint64 bytes_sent);
 
   // Set a new send window offset.
-  // Returns true if this changes send_window_offset_, and false in the case
-  // where |new_send_window| is <= send_window_offset_.
+  // Returns true if this increases send_window_offset_ and is now blocked.
   bool UpdateSendWindowOffset(uint64 new_send_window_offset);
 
   // Returns the current available send window.

net/quic/quic_session.cc

@@ -533,7 +533,9 @@ void QuicSession::OnNewStreamFlowControlWindow(uint32 new_window) {
   }
   for (DataStreamMap::iterator it = stream_map_.begin();
        it != stream_map_.end(); ++it) {
-    it->second->flow_controller()->UpdateSendWindowOffset(new_window);
+    if (it->second->flow_controller()->UpdateSendWindowOffset(new_window)) {
+      it->second->OnCanWrite();
+    }
   }
 }
 

net/quic/quic_session_test.cc

@@ -644,6 +644,9 @@ TEST_P(QuicSessionTest, HandshakeUnblocksFlowControlBlockedStream) {
   stream2->SendBody(body, false);
   EXPECT_TRUE(stream2->flow_controller()->IsBlocked());
 
+  // The handshake message will call OnCanWrite, so the stream can resume
+  // writing.
+  EXPECT_CALL(*stream2, OnCanWrite());
   // Now complete the crypto handshake, resulting in an increased flow control
   // send window.
   CryptoHandshakeMessage msg;

net/quic/reliable_quic_stream.cc

@@ -479,7 +479,6 @@ void ReliableQuicStream::OnWindowUpdateFrame(
     DLOG(DFATAL) << "Flow control not enabled! " << version();
     return;
   }
-
   if (flow_controller_.UpdateSendWindowOffset(frame.byte_offset)) {
     // We can write again!
     // TODO(rjshade): This does not respect priorities (e.g. multiple