New CPAT support in DataReductionProxyConfig guarded by feature flag.

components/data_reduction_proxy/core/common/data_reduction_proxy_features.cc

Index: components/data_reduction_proxy/core/common/data_reduction_proxy_features.cc
diff --git a/components/data_reduction_proxy/core/common/data_reduction_proxy_features.cc b/components/data_reduction_proxy/core/common/data_reduction_proxy_features.cc
index fd4f3f60cca2f55e91c04d8d235687f79d8d032b..4d5a8c8fa32ccbdb098237d9ea2836a97ed4d940 100644
--- a/components/data_reduction_proxy/core/common/data_reduction_proxy_features.cc
+++ b/components/data_reduction_proxy/core/common/data_reduction_proxy_features.cc
@@ -15,5 +15,11 @@ const base::Feature kDataReductionMainMenu{"DataReductionProxyMainMenu",
 const base::Feature kDataReductionSiteBreakdown{
     "DataReductionProxySiteBreakdown", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Enables letting proxy server decide on transformations vs. client

[bengr, 2017/05/23 17:51:25]

Please rewrite to make this clearer:

// Enables a new version of the data reduction proxy protocol where the server
// decides if a server-generated preview should be served. The previous
// version required the client to make this decision. The new protocol relies
// on updates primarily to the Chrome-Proxy-Accept-Transform header.

[dougarnett, 2017/05/23 18:27:44]

Done.

+// deciding locally by effective connection type. Intended to be used to
+// enable newer CPAT protocol to the proxy server.
+const base::Feature kDataReductionProxyDecidesTransform{
+    "DataReductionProxyDecidesTransform", base::FEATURE_DISABLED_BY_DEFAULT};
+
 }  // namespace features
 }  // namespace data_reduction_proxy