Adding an Android about:flags feature for offline previews

components/previews/core/previews_experiments.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 <string>
 
+#include "base/feature_list.h"
 #include "base/logging.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/field_trial_params.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
+#include "components/previews/core/previews_features.h"
 
 namespace previews {
 
 namespace {
 
 // The group of client-side previews experiments. Actually, this group is only
 // expected to control one PreviewsType (OFFLINE) as well as the blacklist.
 // Other PreviewsType's will be control by different field trial groups.
 const char kClientSidePreviewsFieldTrial[] = "ClientSidePreviews";
 
@@ skipping 105 matching lines @@
 }
 
 net::EffectiveConnectionType EffectiveConnectionTypeThresholdForOffline() {
   return GetParamValueAsECT(kClientSidePreviewsFieldTrial,
                             kEffectiveConnectionTypeThreshold,
                             net::EFFECTIVE_CONNECTION_TYPE_SLOW_2G);
 }
 
 bool IsOfflinePreviewsEnabled() {
   //  Check if "show_offline_pages" is set to "true".
-  return IsIncludedInClientSidePreviewsExperimentsFieldTrial() &&
-         base::GetFieldTrialParamValue(kClientSidePreviewsFieldTrial,
-                                       kOfflinePagesSlowNetwork) ==
-             kExperimentEnabled;
+  return base::FeatureList::IsEnabled(features::kOfflinePreviews) ||
+         (IsIncludedInClientSidePreviewsExperimentsFieldTrial() &&

[tbansal1, 2017/05/03 17:35:19]

IIUC, this is not required anymore. Can we delete this?

[RyanSturm, 2017/05/03 21:26:25]

Not sure what you mean. I have to adjust the finch trials to have a seperate
case for "OfflinePreviews:enabled" and "OfflinePreviews:disabled"

[tbansal1, 2017/05/03 22:54:04]

Got it. In that case, should
IsIncludedInClientSidePreviewsExperimentsFieldTrial() also be returning true
when OfflinePreviews is enabled using AboutFlags. or, just make it private?

The comment for that method says:
// Returns true if any client-side previews experiment is active.

+          base::GetFieldTrialParamValue(kClientSidePreviewsFieldTrial,
+                                        kOfflinePagesSlowNetwork) ==
+              kExperimentEnabled);
 }
 
 int OfflinePreviewsVersion() {
   return GetParamValueAsInt(kClientSidePreviewsFieldTrial, kVersion, 0);
 }
 
 bool IsClientLoFiEnabled() {
   return base::StartsWith(
       base::FieldTrialList::FindFullName(kClientLoFiExperimentName), kEnabled,
       base::CompareCase::SENSITIVE);
@@ skipping 14 matching lines @@
 bool IsIncludedInClientSidePreviewsExperimentsFieldTrial() {
   // By convention, an experiment in the client-side previews study enables use
   // of at least one client-side previews optimization if its name begins with
   // "Enabled."
   return base::StartsWith(
       base::FieldTrialList::FindFullName(kClientSidePreviewsFieldTrial),
       kEnabled, base::CompareCase::SENSITIVE);
 }
 
 }  // namespace previews