Allow LPR ECT Threshold to be configurable by field trial

Keeps the 2G default.

Bug: 1010979
Change-Id: I00cff02cfaab075017905a3f64372e36ba97fdfb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1837529
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702538}

chrome/browser/previews/previews_lite_page_redirect_predictor.cc

@@ -74,18 +74,17 @@ bool PreviewsLitePageRedirectPredictor::ECTIsSlow() const {
   if (!g_browser_process->network_quality_tracker())
     return false;
 
-  switch (g_browser_process->network_quality_tracker()
-              ->GetEffectiveConnectionType()) {
-    case net::EFFECTIVE_CONNECTION_TYPE_SLOW_2G:
-    case net::EFFECTIVE_CONNECTION_TYPE_2G:
-      return true;
-    case net::EFFECTIVE_CONNECTION_TYPE_3G:
-    case net::EFFECTIVE_CONNECTION_TYPE_4G:
-    case net::EFFECTIVE_CONNECTION_TYPE_UNKNOWN:
-    case net::EFFECTIVE_CONNECTION_TYPE_OFFLINE:
-    case net::EFFECTIVE_CONNECTION_TYPE_LAST:
+  net::EffectiveConnectionType ect =
+      g_browser_process->network_quality_tracker()
+          ->GetEffectiveConnectionType();
+
+  if (ect == net::EFFECTIVE_CONNECTION_TYPE_UNKNOWN ||
+      ect == net::EFFECTIVE_CONNECTION_TYPE_OFFLINE) {
     return false;
   }
+
+  return ect <= previews::params::
+                    LitePageRedirectPreviewPreresolvePreconnectECTThreshold();
 }
 
 bool PreviewsLitePageRedirectPredictor::PageIsBlacklisted(

components/previews/core/previews_experiments.cc

@@ -249,6 +249,13 @@ base::TimeDelta LitePageRedirectPreviewPreresolvePreconnectInterval() {
       "preresolveconnect_interval_in_seconds", 60));
 }
 
+net::EffectiveConnectionType
+LitePageRedirectPreviewPreresolvePreconnectECTThreshold() {
+  return GetParamValueAsECTByFeature(features::kLitePageServerPreviews,
+                                     "preresolveconnect_ect_threshold",
+                                     net::EFFECTIVE_CONNECTION_TYPE_2G);
+}
+
 base::TimeDelta LitePageRedirectPreviewProbeInterval() {
   return base::TimeDelta::FromSeconds(base::GetFieldTrialParamByFeatureAsInt(
       features::kLitePageServerPreviews, "probe_interval_in_seconds", 30));

components/previews/core/previews_experiments.h

@@ -149,6 +149,11 @@ GURL LitePageRedirectProbeURL();
 // server or the origin.
 base::TimeDelta LitePageRedirectPreviewPreresolvePreconnectInterval();
 
+// The ect threshold at which, or below, we should preresolve or preconnect for
+// lite page redirect previews.
+net::EffectiveConnectionType
+LitePageRedirectPreviewPreresolvePreconnectECTThreshold();
+
 // The duration in between probes to the lite page redirect server.
 base::TimeDelta LitePageRedirectPreviewProbeInterval();