Change IsolateNatives.computeThisScript to use captured value of document.currentScript.

dart/sdk/lib/_internal/compiler/implementation/lib/isolate_helper.dart

Index: dart/sdk/lib/_internal/compiler/implementation/lib/isolate_helper.dart
diff --git a/dart/sdk/lib/_internal/compiler/implementation/lib/isolate_helper.dart b/dart/sdk/lib/_internal/compiler/implementation/lib/isolate_helper.dart
index d25c058fbc80ad2449528eb3a4cd616d56953a0c..8efe55851492336dc38467b2ead0cf14cc75f579 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/lib/isolate_helper.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/lib/isolate_helper.dart
@@ -12,7 +12,9 @@ import 'dart:_js_helper' show convertDartClosureToJS,
 import 'dart:_foreign_helper' show DART_CLOSURE_TO_JS,
                                    JS,
                                    JS_CREATE_ISOLATE,
-                                   JS_SET_CURRENT_ISOLATE;
+                                   JS_CURRENT_ISOLATE,
+                                   JS_SET_CURRENT_ISOLATE,
+                                   IsolateContext;
 
 ReceivePort lazyPort;
 
@@ -202,7 +204,7 @@ class _Manager {
 }
 
 /** Context information tracked for each isolate. */
-class _IsolateContext {
+class _IsolateContext implements IsolateContext {
   /** Current isolate id. */
   int id;
 
@@ -406,19 +408,21 @@ class IsolateNatives {
    * JavaScript workers.
    */
   static String computeThisScript() {
-    // TODO(ahe): The following works in Firefox during loading of the
-    // script, and is being considered for the standard.
-    // if (JS('String', 'typeof document') == 'object') {
-    //   var currentScript = JS('', 'document.currentScript');
-    //   if (JS('String', 'typeof #', currentScript) == 'object') {
-    //     return JS('String', '#.src', currentScript);
-    //   }
-    // }
+    var currentScript =
+        JS('', r'#.$currentScript', JS_CURRENT_ISOLATE().isolateStatics);
+    if (currentScript != null) {
+      return JS('String', 'String(#.src)', currentScript);
+    }
+
+    // TODO(ahe): The following is for supporting command-line engines
+    // such as d8 and jsshell. We should move this code to a helper
+    // library that is only loaded when testing on those engines.
 
     var stack = JS('String|Null', 'new Error().stack');
     if (stack == null) {
       // According to Internet Explorer documentation, the stack
-      // property is not set until the exception is thrown.
+      // property is not set until the exception is thrown. The stack
+      // property was not provided until IE10.

[ngeoffray, 2013/02/19 15:22:26]

But this code is just relevant to command line engines, according to your
comment above.

[ahe, 2013/02/19 15:50:37]

This comment is correct, and should help people understand the problem if they
try to restore this code rather than moving it to a helper library.

[ngeoffray, 2013/02/19 16:00:02]

Even if it's correct, it is confusing, because it's code that will not be used
for browsers.

[ahe, 2013/02/19 16:33:35]

Now I have a problem. I certainly don't want to create confusion, but I really
think it is simpler to refer to the browser name (that are well-known to most),
rather than code names of engines and command lines.

What is worse, "cscript" and "wscript" are really not JavaScript engines. They
are general programs that allow you to execute scripts in many languages
(including Visual Basic and JavaScript).

       stack = JS('String',
                  '(function() {'
                  'try { throw new Error() } catch(e) { return e.stack }'