fix: some websites using WebComponents V0 not loading (#21866)

Co-authored-by: Shelley Vohr <[email protected]>

shell/browser/feature_list.cc

@@ -27,6 +27,13 @@ void InitializeFeatureList() {
   // when node integration is enabled.
   disable_features +=
       std::string(",") + features::kSpareRendererForSitePerProcess.name;
+
+  // https://www.polymer-project.org/blog/2018-10-02-webcomponents-v0-deprecations
+  // https://chromium-review.googlesource.com/c/chromium/src/+/1869562
+  // Any website which uses older WebComponents will fail in without this
+  // enabled, since Electron does not support origin trials.
+  enable_features += std::string(",") + "WebComponentsV0Enabled";
+
 #if !BUILDFLAG(ENABLE_PICTURE_IN_PICTURE)
   disable_features += std::string(",") + media::kPictureInPicture.name;
 #endif