Adding a new component, Previews.

components/previews/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/previews_experiments.h"
+
+#include <map>
+#include <string>
+
+#include "base/metrics/field_trial.h"
+#include "components/variations/variations_associated_data.h"
+
+namespace {
+
+// The group of client side previews experiments.
+const char kClientSideExperimentsFieldTrial[] =
+    "DataReductionProxyClientSideExperimentsFieldTrial";

[tbansal1, 2016/07/26 20:11:37]

I do not think that the field trial name should contain DRP.

s/DataReductionProxyClientSideExperimentsFieldTrial/ClientSidePreviewsFieldTrial/
maybe?

[RyanSturm, 2016/07/26 21:56:52]

Done.

+
+const char kEnabled[] = "Enabled";
+
+// Allow offline pages to show for prohibitively slow networks.
+const char kOfflinePagesSlowNetwork[] = "show_offline_pages";
+
+}  // namespace
+
+namespace previews {
+
+bool IsIncludedInClientSidePreviewsExperimentsFieldTrial() {
+  return base::FieldTrialList::FindFullName(kClientSideExperimentsFieldTrial) ==

[tbansal1, 2016/07/26 20:11:37]

Check if prefix is kEnabled (instead of exact matching)

[RyanSturm, 2016/07/26 21:56:52]

Done.

+         kEnabled;
+}
+
+bool IsIncludedInOfflinePagesSlowConnectionFieldTrial() {
+  if (!IsIncludedInClientSidePreviewsExperimentsFieldTrial())
+    return false;
+  std::map<std::string, std::string> client_side_params;
+  if (!variations::GetVariationParams(kClientSideExperimentsFieldTrial,
+                                      &client_side_params))

[tbansal1, 2016/07/26 20:11:37]

Add braces

[RyanSturm, 2016/07/26 21:56:52]

Done.

+    return false;
+  std::map<std::string, std::string>::const_iterator it =
+      client_side_params.find(kOfflinePagesSlowNetwork);
+  if (it == client_side_params.end())
+    return false;
+  return it->second == "1";

[tbansal1, 2016/07/26 20:11:37]

s/"1"/"true"/

[tbansal1, 2016/07/26 20:11:37]

nit: May be combine with above:
return it != ..end() && it->second == "true";

[RyanSturm, 2016/07/26 21:56:52]

Done.

[RyanSturm, 2016/07/26 21:56:52]

Done.

+}
+
+}  // namespace previews