Add an about:flag to support alternative data saver features

components/data_reduction_proxy/core/browser/data_reduction_proxy_request_options.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 "components/data_reduction_proxy/core/browser/data_reduction_proxy_request_options.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/safe_sprintf.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_tokenizer.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "components/data_reduction_proxy/core/browser/data_reduction_proxy_config.h"
+#include "components/data_reduction_proxy/core/common/data_reduction_proxy_features.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_headers.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_params.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_switches.h"
 #include "components/variations/variations_associated_data.h"
 #include "crypto/random.h"
 #include "net/base/host_port_pair.h"
 #include "net/base/load_flags.h"
 #include "net/proxy/proxy_server.h"
 #include "net/url_request/url_request.h"
 
@@ skipping 63 matching lines @@
   // Called on the UI thread, but should be checked on the IO thread.
   thread_checker_.DetachFromThread();
 }
 
 std::string DataReductionProxyRequestOptions::GetHeaderValueForTesting() const {
   DCHECK(thread_checker_.CalledOnValidThread());
   return header_value_;
 }
 
 void DataReductionProxyRequestOptions::UpdateExperiments() {
-  // TODO(bengr): Simplify this so there's only one way to set experiment via
-  // flags. See crbug.com/656195.
+  experiments_.clear();
   std::string experiments =
       base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
           data_reduction_proxy::switches::kDataReductionProxyExperiment);
 
+  // The command line override takes precedence over field trial "exp"
+  // directives.
   if (!experiments.empty()) {
     base::StringTokenizer experiment_tokenizer(experiments, ", ");
     experiment_tokenizer.set_quote_chars("\"");
     while (experiment_tokenizer.GetNext()) {
       if (!experiment_tokenizer.token().empty())
         experiments_.push_back(experiment_tokenizer.token());
     }
+  } else if (params::AreLitePagesEnabledViaFlags()) {
+    experiments_.push_back(chrome_proxy_lite_page_ignore_blacklist());
   } else {
+    // If no other "exp" directive is forced by flags, add the field trial
+    // value.
     AddServerExperimentFromFieldTrial();
   }
 
   RegenerateRequestHeaderValue();

[tbansal1, 2017/05/23 23:13:34]

nit: DCHECK_GE(1, experiments_.size());

[RyanSturm, 2017/05/23 23:18:11]

Acknowledged.

 }
 
 void DataReductionProxyRequestOptions::AddServerExperimentFromFieldTrial() {
   if (!params::IsIncludedInServerExperimentsFieldTrial())
     return;
   const std::string server_experiment = variations::GetVariationParamValue(
       params::GetServerExperimentsFieldTrialName(), kExperimentsOption);
   if (!server_experiment.empty())
     experiments_.push_back(server_experiment);
 }
@@ skipping 185 matching lines @@
   // Caller should not depend on order.
   return ++current_page_id_;
 }
 
 void DataReductionProxyRequestOptions::ResetPageId() {
   // Caller should not depend on reset setting the page ID to 0.
   current_page_id_ = 0;
 }
 
 }  // namespace data_reduction_proxy