Correcting the version field in the Chrome-Proxy header to be the chromium build and patch number.

chrome/browser/net/spdyproxy/data_reduction_proxy_chrome_settings.cc

 // Copyright 2014 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 "chrome/browser/net/spdyproxy/data_reduction_proxy_chrome_settings.h"
 
+#include "base/strings/string_split.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/net/spdyproxy/data_reduction_proxy_chrome_configurator.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_manager.h"
 #include "components/data_reduction_proxy/browser/data_reduction_proxy_configurator.h"
 #include "components/data_reduction_proxy/browser/data_reduction_proxy_params.h"
 #include "components/data_reduction_proxy/browser/data_reduction_proxy_settings.h"
 
 using data_reduction_proxy::DataReductionProxyParams;
 using data_reduction_proxy::DataReductionProxySettings;
@@ skipping 14 matching lines @@
       configurator(new DataReductionProxyChromeConfigurator(prefs));
   SetProxyConfigurator(configurator.Pass());
   DataReductionProxySettings::InitDataReductionProxySettings(
       prefs,
       g_browser_process->local_state(),
       ProfileManager::GetActiveUserProfile()->GetRequestContext());
 
   SetDataReductionProxyAlternativeEnabled(
       DataReductionProxyParams::IsIncludedInAlternativeFieldTrial());
 }
+
+// static
+std::string DataReductionProxyChromeSettings::GetBuildAndPatchNumber(
+    const std::string& version) {
+  std::vector<std::string> version_parts;
+  base::SplitString(version, '.', &version_parts);

[bengr, 2014/07/31 18:22:40]

You should check that the vector size is 4.
Optional: for symmetry, you could erase the first two elements and then call
JoinString

[megjablon, 2014/07/31 20:48:36]

Done.

+  return version_parts[2] + "." + version_parts[3];
+}