Revert change 7506 to check on build failure.

bin/gen_snapshot.cc

Index: bin/gen_snapshot.cc
===================================================================
--- bin/gen_snapshot.cc	(revision 7506)
+++ bin/gen_snapshot.cc	(working copy)
@@ -157,6 +157,7 @@
 
   return Dart_LoadScript(url,
                          source,
+                         CreateSnapshotLibraryTagHandler,
                          import_map);
 }
 
@@ -276,29 +277,19 @@
   ASSERT(snapshot_filename != NULL);
   // Load up the script before a snapshot is created.
   if (app_script_name != NULL) {
-    // Set up the library tag handler for this isolate.
-    result = Dart_SetLibraryTagHandler(CreateSnapshotLibraryTagHandler);
-    if (Dart_IsError(result)) {
-      fprintf(stderr, "%s", Dart_GetError(result));
-      Dart_ExitScope();
-      Dart_ShutdownIsolate();
-      exit(255);
-    }
     // Load the specified script.
     library = LoadSnapshotCreationScript(app_script_name);
     VerifyLoaded(library);
   } else {
-    // Set up the library tag handler for this isolate.
-    result = Dart_SetLibraryTagHandler(BuiltinLibraryTagHandler);
-    if (Dart_IsError(result)) {
-      fprintf(stderr, "%s", Dart_GetError(result));
-      Dart_ExitScope();
-      Dart_ShutdownIsolate();
-      exit(255);
-    }
+    // Load a dummy script as the script to setup the tag handler.
+    Dart_Handle empty_string = Dart_NewString("");
+    library = Dart_LoadScript(empty_string,
+                                      empty_string,
+                                      BuiltinLibraryTagHandler,
+                                      Dart_Null());
+    VerifyLoaded(library);
     // This is a generic dart snapshot which needs builtin library setup.
-    Dart_Handle library =
-        LoadGenericSnapshotCreationScript(Builtin::kBuiltinLibrary);
+    library = LoadGenericSnapshotCreationScript(Builtin::kBuiltinLibrary);
     VerifyLoaded(library);
     library = LoadGenericSnapshotCreationScript(Builtin::kIOLibrary);
     VerifyLoaded(library);