[Sync] Enable Compression from Client to Server by experiment

components/sync/engine/net/http_bridge.cc

 // 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.
 
 #include "components/sync/engine/net/http_bridge.h"
 
 #include <stddef.h>
 
 #include <vector>
 
 #include "base/bit_cast.h"
 #include "base/location.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/sync/base/cancelation_signal.h"
 #include "net/base/load_flags.h"
 #include "net/base/net_errors.h"
 #include "net/http/http_cache.h"
 #include "net/http/http_network_layer.h"
 #include "net/http/http_request_headers.h"
 #include "net/http/http_response_headers.h"
 #include "net/url_request/static_http_user_agent_settings.h"
 #include "net/url_request/url_fetcher.h"
 #include "net/url_request/url_request_job_factory_impl.h"
 #include "net/url_request/url_request_status.h"
+#include "third_party/zlib/google/compression_utils.h"
 
 namespace syncer {
 
 namespace {
 
 // It's possible for an http request to be silently stalled. We set a time
 // limit for all http requests, beyond which the request is cancelled and
 // treated as a transient failure.
 const int kMaxHttpRequestTimeSeconds = 60 * 5;  // 5 minutes.
 
@@ skipping 14 matching lines @@
     int64_t compressed_content_length,
     int64_t original_content_length) {
   UMA_HISTOGRAM_COUNTS("Sync.ResponseContentLength.Compressed",
                        compressed_content_length);
   UMA_HISTOGRAM_COUNTS("Sync.ResponseContentLength.Original",
                        original_content_length);
 }
 
 }  // namespace
 
+// Enables compression of messages from client to server.
+const base::Feature kSyncClientToServerCompression{
+    "EnableSyncClientToServerCompression", base::FEATURE_DISABLED_BY_DEFAULT};
+
 HttpBridgeFactory::HttpBridgeFactory(
     const scoped_refptr<net::URLRequestContextGetter>& request_context_getter,
     const NetworkTimeUpdateCallback& network_time_update_callback,
     CancelationSignal* cancelation_signal)
     : request_context_getter_(request_context_getter),
       network_time_update_callback_(network_time_update_callback),
       cancelation_signal_(cancelation_signal) {
   // Registration should never fail.  This should happen on the UI thread during
   // init.  It would be impossible for a shutdown to have been requested at this
   // point.
@@ skipping 157 matching lines @@
   DCHECK(request_context_getter_.get());
   fetch_state_.start_time = base::Time::Now();
   fetch_state_.url_poster =
       net::URLFetcher::Create(url_for_request_, net::URLFetcher::POST, this)
           .release();
   if (!bind_to_tracker_callback_.is_null())
     bind_to_tracker_callback_.Run(fetch_state_.url_poster);
   fetch_state_.url_poster->SetRequestContext(request_context_getter_.get());
   fetch_state_.url_poster->SetExtraRequestHeaders(extra_headers_);
 
-  fetch_state_.url_poster->SetUploadData(content_type_, request_content_);
-  RecordSyncRequestContentLengthHistograms(request_content_.size(),
+  std::string request_to_send;
+  if (base::FeatureList::IsEnabled(kSyncClientToServerCompression)) {
+    compression::GzipCompress(request_content_, &request_to_send);
+    fetch_state_.url_poster->AddExtraRequestHeader("Content-Encoding: gzip");
+  } else {
+    request_to_send = request_content_;
+  }
+  fetch_state_.url_poster->SetUploadData(content_type_, request_to_send);
+  RecordSyncRequestContentLengthHistograms(request_to_send.size(),
                                            request_content_.size());
 
   fetch_state_.url_poster->AddExtraRequestHeader(base::StringPrintf(
       "%s: %s", net::HttpRequestHeaders::kUserAgent, user_agent_.c_str()));
   fetch_state_.url_poster->SetLoadFlags(
       net::LOAD_BYPASS_CACHE | net::LOAD_DISABLE_CACHE |
       net::LOAD_DO_NOT_SAVE_COOKIES | net::LOAD_DO_NOT_SEND_COOKIES);
 
   fetch_state_.url_poster->Start();
 }
@@ skipping 182 matching lines @@
   int64_t sane_time_ms = 0;
   if (base::StringToInt64(sane_time_str, &sane_time_ms)) {
     network_time_update_callback_.Run(
         base::Time::FromJsTime(sane_time_ms),
         base::TimeDelta::FromMilliseconds(1),
         fetch_state_.end_time - fetch_state_.start_time);
   }
 }
 
 }  // namespace syncer