Hard coded finch config for Popular site

ios/chrome/browser/ios_chrome_field_trials.cc

Index: ios/chrome/browser/ios_chrome_field_trials.cc
diff --git a/ios/chrome/browser/ios_chrome_field_trials.cc b/ios/chrome/browser/ios_chrome_field_trials.cc
index fb1b5f33ce07d29c1719228e5836e606d16ce5cd..d1ef899ef57b8939fcf7fd27bf53cdb699d269c4 100644
--- a/ios/chrome/browser/ios_chrome_field_trials.cc
+++ b/ios/chrome/browser/ios_chrome_field_trials.cc
@@ -5,8 +5,15 @@
 #include "ios/chrome/browser/ios_chrome_field_trials.h"
 
 #include "base/metrics/field_trial.h"
+#include "components/ntp_tiles/field_trial.h"
+#include "components/version_info/version_info.h"
+#include "ios/chrome/common/channel_info.h"
 
 void SetupIOSFieldTrials() {
   // Activate the iOS tab eviction dynamic field trials.
   base::FieldTrialList::FindValue("TabEviction");
+
+  // Setup a field trial for a first run experiment on Popular sites.
+  ntp_tiles::SetUpFirstLaunchFieldTrial(GetChannel() ==
+                                        version_info::Channel::STABLE);
 }