[Sync] Enable Compression from Client to Server by experiment

components/sync/engine/net/http_bridge.h

 // Copyright 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 COMPONENTS_SYNC_ENGINE_NET_HTTP_BRIDGE_H_
 #define COMPONENTS_SYNC_ENGINE_NET_HTTP_BRIDGE_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 
 #include "base/compiler_specific.h"
+#include "base/feature_list.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/lock.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/thread_checker.h"
 #include "base/timer/timer.h"
 #include "components/sync/base/cancelation_observer.h"
 #include "components/sync/engine/net/http_post_provider_factory.h"
 #include "components/sync/engine/net/http_post_provider_interface.h"
 #include "components/sync/engine/net/network_time_update_callback.h"
 #include "net/url_request/url_fetcher_delegate.h"
 #include "net/url_request/url_request_context.h"
 #include "net/url_request/url_request_context_getter.h"
 #include "url/gurl.h"
 
 class HttpBridgeTest;
 
 namespace net {
 class HttpResponseHeaders;
 class HttpUserAgentSettings;
 class URLFetcher;
 class URLRequestJobFactory;
 }
 
 namespace syncer {
 
 class CancelationSignal;
+extern const base::Feature kSyncClientToServerCompression;
 
 // A bridge between the syncer and Chromium HTTP layers.
 // Provides a way for the sync backend to use Chromium directly for HTTP
 // requests rather than depending on a third party provider (e.g libcurl).
 // This is a one-time use bridge. Create one for each request you want to make.
 // It is RefCountedThreadSafe because it can PostTask to the io loop, and thus
 // needs to stick around across context switches, etc.
 class HttpBridge : public base::RefCountedThreadSafe<HttpBridge>,
                    public HttpPostProviderInterface,
                    public net::URLFetcherDelegate {
@@ skipping 173 matching lines @@
   // A callback to tag Sync request to be able to record data use of this
   // service by data_use_measurement component.
   BindToTrackerCallback bind_to_tracker_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(HttpBridgeFactory);
 };
 
 }  //  namespace syncer
 
 #endif  // COMPONENTS_SYNC_ENGINE_NET_HTTP_BRIDGE_H_