Handle "//# sourceURL" comments in the Parser instead of the JS.

src/heap.h

Index: src/heap.h
diff --git a/src/heap.h b/src/heap.h
index 3945515e01b1f9bdda347fa68c9fe18c13194829..6037338a89a6d7687ae274dffba2551d66357b56 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -292,6 +292,8 @@ namespace internal {
   V(nan_string, "NaN")                                                   \
   V(RegExp_string, "RegExp")                                             \
   V(source_string, "source")                                             \
+  V(source_url_string, "source_url")                                     \
+  V(source_mapping_url_string, "source_mapping_url")                     \
   V(global_string, "global")                                             \
   V(ignore_case_string, "ignoreCase")                                    \
   V(multiline_string, "multiline")                                       \