dart2js: Allow 'throw' when inlining

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

Index: sdk/lib/_internal/compiler/implementation/lib/js_helper.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/js_helper.dart b/sdk/lib/_internal/compiler/implementation/lib/js_helper.dart
index badbb4dd1186584f34d1bf51708783def14f5ac9..c53f88f2a14702bf5ce91516a6314e375d8fa342 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/js_helper.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/js_helper.dart
@@ -634,6 +634,15 @@ $throw(ex) {
 }
 
 /**
+ * This version of the $throw helper actually does the throw too.  It is
+ * possible to call this in a JS expression context, where the throw statement
+ * is not allowed.

[ngeoffray, 2013/04/10 12:06:39]

Please also add that a helper is never inlined. If it was to be inlined, we
could not do this trick.

[erikcorry, 2013/04/10 12:52:32]

Done.

+ */
+throwExpression(ex) {
+  JS('void', 'throw #', $throw(ex));
+}
+
+/**
  * Wrapper class for throwing exceptions.
  */
 class DartError {