isolate: fix how we get the current script now that frog automatically wraps the

lib/isolate/frog/natives.js

Index: lib/isolate/frog/natives.js
diff --git a/lib/isolate/frog/natives.js b/lib/isolate/frog/natives.js
index 62ad76e63f7af6254b94c82dccd00f5514fb9fba..2808ecb2cc9aeaa989dd5e06d30d8e2bdb3e8e1c 100644
--- a/lib/isolate/frog/natives.js
+++ b/lib/isolate/frog/natives.js
@@ -7,6 +7,10 @@
 var $globalThis = this;
 var $globals = null;
 var $globalState = null;
+var $thisScriptUrl = null;
+var $isWorker = typeof ($globalThis['importScripts']) != 'undefined';
+var $supportsWorkers =
+    $isWorker || ((typeof $globalThis['Worker']) != 'undefined');
 function $initGlobals(context) { context.isolateStatics = {}; }
 function $setGlobals(context) { $globals = context.isolateStatics; }
 
@@ -39,3 +43,21 @@ Function.prototype.wrap$call$1 = function() {
   this.wrap$call$1 = function() { return this.wrap$1; };
   return this.wrap$1;
 };
+
+$thisScriptUrl = (function () {
+  if (!$supportsWorkers || $isWorker) return (void 0);
+
+  // TODO(5334778): Find a cross-platform non-brittle way of getting the
+  // currently running script.
+  var scripts = document.getElementsByTagName('script');
+  // The scripts variable only contains the scripts that have already been
+  // executed. The last one is the currently running script.
+  var script = scripts[scripts.length - 1];
+  var src = script && script.src;
+  if (!src) {
+    // TODO()
+    src = "FIXME:5407062" + "_" + Math.random().toString();
+    if (script) script.src = src;
+  }
+  return src;
+})();