Makes migration on write error asynchronous to avoid reentrancy issues

net/quic/chromium/quic_chromium_client_session.h

Index: net/quic/chromium/quic_chromium_client_session.h
diff --git a/net/quic/chromium/quic_chromium_client_session.h b/net/quic/chromium/quic_chromium_client_session.h
index b51fc440d57c5cfafe5e76936bb6f87e0088f1a7..d3eb0fd83f260753c00f7eb2017e6414bcb6a9e3 100644
--- a/net/quic/chromium/quic_chromium_client_session.h
+++ b/net/quic/chromium/quic_chromium_client_session.h
@@ -253,19 +253,25 @@ class NET_EXPORT_PRIVATE QuicChromiumClientSession
 
   QuicDisabledReason disabled_reason() const { return disabled_reason_; }
 
+  // Attempts to migrate session when a write error is encountered.
+  void MigrateSessionOnWriteError();
+
+  // Helper method that writes a packet on the new socket after
+  // migration completes. If not null, the packet_ member is written,
+  // else a PING packet is written.

[Ryan Hamilton, 2016/09/12 00:52:18]

nit: s/else/otherwise/

[Jana, 2016/09/12 21:08:02]

Done.

+  void WriteToNewSocket();
+
   // Migrates session onto new socket, i.e., starts reading from
   // |socket| in addition to any previous sockets, and sets |writer|
   // to be the new default writer. Returns true if socket was
   // successfully added to the session and the session was
-  // successfully migrated to using the new socket. If not null,
-  // |packet| is sent on the new network, else a PING frame is
-  // sent. Returns true on successful migration, or false if number of
-  // migrations exceeds kMaxReadersPerQuicSession.  Takes ownership of
-  // |socket|, |reader|, and |writer|.
+  // successfully migrated to using the new socket. Returns true on
+  // successful migration, or false if number of migrations exceeds
+  // kMaxReadersPerQuicSession. Takes ownership of |socket|, |reader|,
+  // and |writer|.
   bool MigrateToSocket(std::unique_ptr<DatagramClientSocket> socket,
                        std::unique_ptr<QuicChromiumPacketReader> reader,
-                       std::unique_ptr<QuicChromiumPacketWriter> writer,
-                       scoped_refptr<StringIOBuffer> packet);
+                       std::unique_ptr<QuicChromiumPacketWriter> writer);
 
   // Populates network error details for this session.
   void PopulateNetErrorDetails(NetErrorDetails* details);
@@ -365,10 +371,11 @@ class NET_EXPORT_PRIVATE QuicChromiumClientSession
   // UMA histogram counters for streams pushed to this session.
   int streams_pushed_count_;
   int streams_pushed_and_claimed_count_;
-  // Return value from packet rewrite packet on new socket. Used
-  // during connection migration on socket write error.
-  int error_code_from_rewrite_;
-  bool use_error_code_from_rewrite_;
+  // Stores packet that witnesses socket write error. This packet is
+  // written to a new socket after migration completes.
+  scoped_refptr<StringIOBuffer> packet_;
+  bool migration_pending_;  // True while migration is underway.
+  bool write_pending_;      // True while post-migration write is underway.
   base::WeakPtrFactory<QuicChromiumClientSession> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(QuicChromiumClientSession);