Adding an Android about:flags feature for offline previews

components/previews/core/previews_experiments_unittest.cc

Index: components/previews/core/previews_experiments_unittest.cc
diff --git a/components/previews/core/previews_experiments_unittest.cc b/components/previews/core/previews_experiments_unittest.cc
index be81b3d7587cb07bed2565227aaa18fc2298688a..3186246326fe5b8423417224428ce92440590b55 100644
--- a/components/previews/core/previews_experiments_unittest.cc
+++ b/components/previews/core/previews_experiments_unittest.cc
@@ -7,6 +7,8 @@
 #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"
@@ -24,7 +26,6 @@ const char kEnabled[] = "Enabled";
 
 // Verifies that we can enable offline previews via field trial.
 TEST(PreviewsExperimentsTest, TestFieldTrialOfflinePage) {
-  EXPECT_FALSE(IsIncludedInClientSidePreviewsExperimentsFieldTrial());
   EXPECT_FALSE(params::IsOfflinePreviewsEnabled());
 
   base::FieldTrialList field_trial_list(nullptr);
@@ -36,11 +37,26 @@ TEST(PreviewsExperimentsTest, TestFieldTrialOfflinePage) {
   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(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_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) {