[DevTools] Flip experiment flag for Payment Handler.

Bug: 980291
Change-Id: I951ce25bb15e17f48b974f30a8b8e074f83f8e32
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1771975
Commit-Queue: Rayan Kanso <[email protected]>
Reviewed-by: Alexei Filippov <[email protected]>
Cr-Original-Commit-Position: refs/heads/master@{#691119}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 63670ec8bd225eb0c5615aa0d0b244905f1c9468
diff --git a/front_end/main/Main.js b/front_end/main/Main.js
index 716f9fc..0c17d6a 100644
--- a/front_end/main/Main.js
+++ b/front_end/main/Main.js
@@ -139,8 +139,12 @@
     const enabledExperiments = Runtime.queryParam('enabledExperiments');
     if (enabledExperiments)
       Runtime.experiments.setServerEnabledExperiments(enabledExperiments.split(';'));
-    Runtime.experiments.setDefaultExperiments(
-        ['backgroundServices', 'backgroundServicesNotifications', 'backgroundServicesPushMessaging']);
+    Runtime.experiments.setDefaultExperiments([
+      'backgroundServices',
+      'backgroundServicesNotifications',
+      'backgroundServicesPushMessaging',
+      'backgroundServicesPaymentHandler',
+    ]);
 
     if (Host.isUnderTest() && Runtime.queryParam('test').includes('live-line-level-heap-profile.js'))
       Runtime.experiments.enableForTest('liveHeapProfile');