Adding a parameter for previews NQE triggering threshold

components/previews/core/previews_experiments.cc

Index: components/previews/core/previews_experiments.cc
diff --git a/components/previews/core/previews_experiments.cc b/components/previews/core/previews_experiments.cc
index 3806bc9c8e8f6084023175e7ff2c222bed53c99f..31bf388a455c272dacc7adb84b8b9e7f94021fb5 100644
--- a/components/previews/core/previews_experiments.cc
+++ b/components/previews/core/previews_experiments.cc
@@ -64,6 +64,12 @@ const char kSingleOptOutDurationInSeconds[] =
 const char kOfflinePreviewFreshnessDurationInDays[] =
     "offline_preview_freshness_duration_in_days";
 
+// The threshold of EffectiveConnectionType above which previews will not be
+// served.
+// See net/nqe/effective_connection_type.h for mapping from int to value.
+const char kEffectiveConnectionTypeThreshold[] =
+    "max_allowed_effective_connection_type";
+
 // The string that corresponds to enabled for the variation param experiments.
 const char kExperimentEnabled[] = "true";
 
@@ -158,6 +164,16 @@ base::TimeDelta OfflinePreviewFreshnessDuration() {
   return base::TimeDelta::FromDays(duration);
 }
 
+net::EffectiveConnectionType EffectiveConnectionTypeThreshold() {
+  std::string param_value = ParamValue(kEffectiveConnectionTypeThreshold);
+  int effective_type_value;
+  if (!base::StringToInt(param_value, &effective_type_value)) {

[tbansal1, 2017/02/02 00:13:40]

You may want to use this function:
https://cs.chromium.org/chromium/src/net/nqe/effective_connection_type.cc?rcl...
if you prefer a more descriptive name in the config files.

[RyanSturm, 2017/02/02 00:22:28]

Done. Thanks.

+    effective_type_value =

[tbansal1, 2017/02/02 00:13:40]

Instead of 2 static casts, may be just return E_C_T_SLOW2G here.

[RyanSturm, 2017/02/02 00:22:28]

Acknowledged.

+        static_cast<int>(net::EFFECTIVE_CONNECTION_TYPE_SLOW_2G);
+  }
+  return static_cast<net::EffectiveConnectionType>(effective_type_value);
+}
+
 }  // namespace params
 
 bool IsIncludedInClientSidePreviewsExperimentsFieldTrial() {