Add an about:flag to support alternative data saver features

components/data_reduction_proxy/core/browser/data_reduction_proxy_request_options_unittest.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 <map>
 #include <memory>
 #include <string>
 #include <vector>
@@ skipping 313 matching lines @@
 
     SetHeaderExpectations(kExpectedSession, kExpectedCredentials, std::string(),
                           kClientStr, kExpectedBuild, kExpectedPatch, kPageId,
                           expected_experiments, &expected_header);
 
     CreateRequestOptions(kVersion);
     VerifyExpectedHeader(expected_header, kPageIdValue);
   }
 }
 
+TEST_F(DataReductionProxyRequestOptionsTest, TestExperimentPrecedence) {
+  // Tests that combinations of configurations that trigger "exp=" directive in
+  // the Chrome-Proxy header have the right precendence, and only append a value
+  // for the highest priority value.
+
+  // Field trial has the lowest priority.
+  std::map<std::string, std::string> server_experiment;
+  server_experiment["exp"] = "foo";
+  ASSERT_TRUE(variations::AssociateVariationParams(
+      params::GetServerExperimentsFieldTrialName(), "enabled",
+      server_experiment));
+
+  base::FieldTrialList field_trial_list(nullptr);
+  base::FieldTrialList::CreateFieldTrial(
+      params::GetServerExperimentsFieldTrialName(), "enabled");
+  std::vector<std::string> expected_experiments;
+  expected_experiments.push_back("foo");
+  std::string expected_header;
+  SetHeaderExpectations(kExpectedSession, kExpectedCredentials, std::string(),
+                        kClientStr, kExpectedBuild, kExpectedPatch, kPageId,
+                        expected_experiments, &expected_header);
+  CreateRequestOptions(kVersion);
+  VerifyExpectedHeader(expected_header, kPageIdValue);
+
+  // "ignore_preview_blacklist" has the next lowest priority.
+  base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+      switches::kDataReductionProxyLoFi,
+      switches::kDataReductionProxyLoFiValueAlwaysOn);
+  base::CommandLine::ForCurrentProcess()->AppendSwitch(
+      switches::kEnableDataReductionProxyLitePage);
+  expected_experiments.clear();
+  expected_experiments.push_back(chrome_proxy_lite_page_ignore_blacklist());
+  SetHeaderExpectations(kExpectedSession, kExpectedCredentials, std::string(),
+                        kClientStr, kExpectedBuild, kExpectedPatch, kPageId,
+                        expected_experiments, &expected_header);
+  CreateRequestOptions(kVersion);
+  VerifyExpectedHeader(expected_header, kPageIdValue);
+
+  // Setting the experiment explicitly has the highest priority.
+  base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+      data_reduction_proxy::switches::kDataReductionProxyExperiment, "bar");
+  expected_experiments.clear();
+  expected_experiments.push_back("bar");
+  SetHeaderExpectations(kExpectedSession, kExpectedCredentials, std::string(),
+                        kClientStr, kExpectedBuild, kExpectedPatch, kPageId,
+                        expected_experiments, &expected_header);
+  CreateRequestOptions(kVersion);
+  VerifyExpectedHeader(expected_header, kPageIdValue);
+}
+
 TEST_F(DataReductionProxyRequestOptionsTest, GetSessionKeyFromRequestHeaders) {
   const struct {
     std::string chrome_proxy_header_key;
     std::string chrome_proxy_header_value;
     std::string expected_session_key;
   } tests[] = {
       {"chrome-proxy", "something=something_else, s=123, key=value", "123"},
       {"chrome-proxy", "something=something_else, s= 123  456 , key=value",
        "123  456"},
       {"chrome-proxy", "something=something_else, s=123456,    key=value",
@@ skipping 30 matching lines @@
   DCHECK_EQ(3u, request_options()->GeneratePageId());
 
   request_options()->SetSecureSession("blah");
 
   DCHECK_EQ(1u, request_options()->GeneratePageId());
   DCHECK_EQ(2u, request_options()->GeneratePageId());
   DCHECK_EQ(3u, request_options()->GeneratePageId());
 }
 
 }  // namespace data_reduction_proxy