Fix plugin install with Polymer 2 and polyfills

In Safari the variable 'src' ends up being 'data:...' valued, while
script.baseURI would be usable, so let's add an if statement to just
use that. 'data:...' is not a suitable input for getPluginNameFromUrl().

Bug: Issue 11128
Change-Id: I83de47382d335cf67f0922c56f1b10a4b252e529
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-public-js-api.js b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-public-js-api.js
index 11c9864..e422b7e 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-public-js-api.js
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-public-js-api.js
@@ -528,7 +528,11 @@
     // HTML import polyfill adds __importElement pointing to the import tag.
     const script = document.currentScript &&
         (document.currentScript.__importElement || document.currentScript);
-    const src = opt_src || (script && (script.src || script.baseURI));
+
+    let src = opt_src || (script && script.src);
+    if (!src || src.startsWith('data:')) {
+      src = script && script.baseURI;
+    }
     const name = getPluginNameFromUrl(src);
 
     if (opt_version && opt_version !== API_VERSION) {