Add 'explicit' to the PacketWriterFactoryAdapter constructor, as

net/quic/quic_dispatcher.h

Index: net/quic/quic_dispatcher.h
diff --git a/net/quic/quic_dispatcher.h b/net/quic/quic_dispatcher.h
index 895f946cd271985f3831c0b07ec08c7a3309396f..c508cb8d914129e3301b60157e442c43e5c934cc 100644
--- a/net/quic/quic_dispatcher.h
+++ b/net/quic/quic_dispatcher.h
@@ -190,7 +190,7 @@ class QuicDispatcher : public QuicBlockedWriterInterface,
   class PacketWriterFactoryAdapter :
     public QuicConnection::PacketWriterFactory {
    public:
-    PacketWriterFactoryAdapter(QuicDispatcher* dispatcher);
+    explicit PacketWriterFactoryAdapter(QuicDispatcher* dispatcher);
     ~PacketWriterFactoryAdapter() override;
 
     QuicPacketWriter* Create(QuicConnection* connection) const override;