Adding an Android about:flags feature for offline previews

components/previews/core/previews_experiments_unittest.cc

 // Copyright 2016 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/previews/core/previews_experiments.h"
 
 #include <map>
 #include <string>
 
+#include "base/feature_list.h"
+#include "base/memory/ptr_util.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/field_trial_params.h"
 #include "base/strings/string_util.h"
 #include "components/variations/variations_associated_data.h"
 
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace previews {
 
 namespace {
@@ skipping 14 matching lines @@
   EXPECT_TRUE(base::AssociateFieldTrialParams(kClientSidePreviewsFieldTrial,
                                               kEnabled, params));
   EXPECT_TRUE(base::FieldTrialList::CreateFieldTrial(
       kClientSidePreviewsFieldTrial, kEnabled));
 
   EXPECT_TRUE(IsIncludedInClientSidePreviewsExperimentsFieldTrial());
   EXPECT_TRUE(params::IsOfflinePreviewsEnabled());
   variations::testing::ClearAllVariationParams();
 }
 
+// Verifies that we can enable offline previews via comand line.
+TEST(PreviewsExperimentsTest, TestCommandLineOfflinePage) {
+  EXPECT_FALSE(IsIncludedInClientSidePreviewsExperimentsFieldTrial());
+  EXPECT_FALSE(params::IsOfflinePreviewsEnabled());
+
+  std::unique_ptr<base::FeatureList> feature_list =
+      base::MakeUnique<base::FeatureList>();
+
+  // The feature is explicitly enabled on the command-line.
+  feature_list->InitializeFromCommandLine("OfflinePreviews", "");
+  base::FeatureList::ClearInstanceForTesting();
+  base::FeatureList::SetInstance(std::move(feature_list));
+
+  EXPECT_FALSE(IsIncludedInClientSidePreviewsExperimentsFieldTrial());
+  EXPECT_TRUE(params::IsOfflinePreviewsEnabled());
+  base::FeatureList::ClearInstanceForTesting();
+}
+
 // Verifies that the default params are correct, and that custom params can be
 // set, for both the previews blacklist and offline previews.
 TEST(PreviewsExperimentsTest, TestParamsForBlackListAndOffline) {
   // Verify that the default params are correct.
   EXPECT_EQ(4u, params::MaxStoredHistoryLengthForPerHostBlackList());
   EXPECT_EQ(10u, params::MaxStoredHistoryLengthForHostIndifferentBlackList());
   EXPECT_EQ(100u, params::MaxInMemoryHostsInBlackList());
   EXPECT_EQ(2, params::PerHostBlackListOptOutThreshold());
   EXPECT_EQ(4, params::HostIndifferentBlackListOptOutThreshold());
   EXPECT_EQ(base::TimeDelta::FromDays(30), params::PerHostBlackListDuration());
@@ skipping 92 matching lines @@
   EXPECT_EQ(10, params::ClientLoFiVersion());
   EXPECT_EQ(net::EFFECTIVE_CONNECTION_TYPE_3G,
             params::EffectiveConnectionTypeThresholdForClientLoFi());
 
   variations::testing::ClearAllVariationParams();
 }
 
 }  // namespace
 
 }  // namespace previews