[Cronet] Enable persistence mode for Sdch

components/cronet/android/cronet_url_request_context_adapter.h

Index: components/cronet/android/cronet_url_request_context_adapter.h
diff --git a/components/cronet/android/cronet_url_request_context_adapter.h b/components/cronet/android/cronet_url_request_context_adapter.h
index 6366c5d03d3df77c4291e2f153bb8e3261368186..d5f0e02f04f68e82ca6bf937b4e6e6e4a605653b 100644
--- a/components/cronet/android/cronet_url_request_context_adapter.h
+++ b/components/cronet/android/cronet_url_request_context_adapter.h
@@ -15,6 +15,7 @@
 #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"
 
 namespace base {
@@ -93,11 +94,20 @@ class CronetURLRequestContextAdapter {
 
   // Network thread is owned by |this|, but is destroyed from java thread.
   base::Thread* network_thread_;
+
+  // File thread should be destroyed last.
+  scoped_ptr<base::Thread> file_thread_;
+
   // |write_to_file_observer_| and |context_| should only be accessed on
   // network thread.
   scoped_ptr<net::WriteToFileNetLogObserver> write_to_file_observer_;
   scoped_ptr<net::URLRequestContext> context_;
   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_;
 
   // Context config is only valid untng context is initialized.