Pass QuicInMemoryCache directly instead of using a singleton.

net/tools/quic/quic_simple_dispatcher.h

 // Copyright (c) 2012 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.
 
 #ifndef NET_TOOLS_QUIC_QUIC_SIMPLE_DISPATCHER_H_
 #define NET_TOOLS_QUIC_QUIC_SIMPLE_DISPATCHER_H_
 
 #include "net/quic/core/quic_server_session_base.h"
 #include "net/tools/quic/quic_dispatcher.h"
+#include "net/tools/quic/quic_in_memory_cache.h"
 
 namespace net {
 
 class QuicSimpleDispatcher : public QuicDispatcher {
  public:
   QuicSimpleDispatcher(
       const QuicConfig& config,
       const QuicCryptoServerConfig* crypto_config,
       QuicVersionManager* version_manager,
       std::unique_ptr<QuicConnectionHelperInterface> helper,
       std::unique_ptr<QuicCryptoServerStream::Helper> session_helper,
-      std::unique_ptr<QuicAlarmFactory> alarm_factory);
+      std::unique_ptr<QuicAlarmFactory> alarm_factory,
+      QuicInMemoryCache* in_memory_cache);
 
   ~QuicSimpleDispatcher() override;
 
  protected:
   QuicServerSessionBase* CreateQuicSession(
       QuicConnectionId connection_id,
       const QuicSocketAddress& client_address) override;
+
+  QuicInMemoryCache* in_memory_cache() { return in_memory_cache_; }
+
+ private:
+  QuicInMemoryCache* in_memory_cache_;  // Unowned.
 };
 
 }  // namespace net
 
 #endif  // NET_TOOLS_QUIC_QUIC_SIMPLE_DISPATCHER_H_