[Cronet] Enable persistence mode for Sdch

components/cronet/android/url_request_context_adapter.h

Index: components/cronet/android/url_request_context_adapter.h
diff --git a/components/cronet/android/url_request_context_adapter.h b/components/cronet/android/url_request_context_adapter.h
index 539a76afde093974f3e59cb3dcb620e5bcfd9527..48cb5c7721f020041188a50ac02eaabfd51d94fa 100644
--- a/components/cronet/android/url_request_context_adapter.h
+++ b/components/cronet/android/url_request_context_adapter.h
@@ -14,6 +14,7 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/prefs/json_pref_store.h"
 #include "base/threading/thread.h"
 #include "net/log/net_log.h"
 #include "net/url_request/url_request_context.h"
@@ -99,14 +100,20 @@ class URLRequestContextAdapter : public net::URLRequestContextGetter {
   // run after context is initialized.
   void StopNetLogHelper();
 
+  base::Thread* network_thread_;
+  scoped_ptr<base::Thread> file_thread_;
+
   scoped_refptr<URLRequestContextAdapterDelegate> delegate_;
   scoped_ptr<net::URLRequestContext> context_;
   std::string user_agent_;
   bool load_disable_cache_;
-  base::Thread* network_thread_;
   scoped_ptr<NetLogObserver> net_log_observer_;
   scoped_ptr<net::WriteToFileNetLogObserver> write_to_file_observer_;
   scoped_ptr<net::ProxyConfigService> proxy_config_service_;
+  // |sdch_owner_| should be destroyed before |json_pref_store_|, because
+  // tearing down |sdch_owner_| forces |json_pref_store_| to flush pending
+  // writes to the disk.
+  scoped_refptr<JsonPrefStore> json_pref_store_;
   scoped_ptr<net::SdchOwner> sdch_owner_;
   scoped_ptr<URLRequestContextConfig> config_;