Update prerender policy for custom tabs

chrome/browser/prerender/prerender_manager.cc

Index: chrome/browser/prerender/prerender_manager.cc
diff --git a/chrome/browser/prerender/prerender_manager.cc b/chrome/browser/prerender/prerender_manager.cc
index f8093165d41e350bb503470ed64c5ced684e2ca0..8fa28e77ccfd0f700589f1023a07c5ba7351e56b 100644
--- a/chrome/browser/prerender/prerender_manager.cc
+++ b/chrome/browser/prerender/prerender_manager.cc
@@ -298,7 +298,19 @@ PrerenderHandle* PrerenderManager::AddPrerenderFromExternalRequest(
     const content::Referrer& referrer,
     SessionStorageNamespace* session_storage_namespace,
     const gfx::Size& size) {
-  return AddPrerender(ORIGIN_EXTERNAL_REQUEST, url, referrer, size,
+  return AddPrerender(
+      ORIGIN_EXTERNAL_REQUEST, url, referrer, size, session_storage_namespace);
+}
+
+PrerenderHandle* PrerenderManager::AddPrerenderOnCellularFromExternalRequest(
+    const GURL& url,
+    const content::Referrer& referrer,
+    SessionStorageNamespace* session_storage_namespace,
+    const gfx::Size& size) {
+  return AddPrerender(ORIGIN_EXTERNAL_REQUEST_FORCED_CELLULAR,
+                      url,
+                      referrer,
+                      size,
                       session_storage_namespace);
 }
 
@@ -934,7 +946,8 @@ PrerenderHandle* PrerenderManager::AddPrerender(
   // histogram tracking.
   histograms_->RecordPrerender(origin, url_arg);
 
-  NetworkPredictionStatus prerendering_status = GetPredictionStatus();
+  NetworkPredictionStatus prerendering_status =
+      GetPredictionStatusForOrigin(origin);
   if (prerendering_status != NetworkPredictionStatus::ENABLED) {
     FinalStatus final_status =
         prerendering_status == NetworkPredictionStatus::DISABLED_DUE_TO_NETWORK
@@ -1283,6 +1296,16 @@ NetworkPredictionStatus PrerenderManager::GetPredictionStatus() const {
   return CanPrefetchAndPrerenderUI(profile_->GetPrefs());
 }
 
+NetworkPredictionStatus PrerenderManager::GetPredictionStatusForOrigin(
+    Origin origin) const {
+  NetworkPredictionStatus prediction_status = GetPredictionStatus();
+  if (prediction_status == NetworkPredictionStatus::DISABLED_DUE_TO_NETWORK
+      && origin == ORIGIN_EXTERNAL_REQUEST_FORCED_CELLULAR) {
+    prediction_status = NetworkPredictionStatus::ENABLED;
+  }
+  return prediction_status;
+}
+
 void PrerenderManager::AddProfileNetworkBytesIfEnabled(int64_t bytes) {
   DCHECK_GE(bytes, 0);
   if (GetPredictionStatus() == NetworkPredictionStatus::ENABLED &&