Start using Dart_PropagateError in the runtime/bin directory.

runtime/bin/gen_snapshot.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // Generate a snapshot file after loading all the scripts specified on the
 // command line.
 
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
@@ skipping 109 matching lines @@
                                                    Dart_Handle import_map) {
   if (!Dart_IsLibrary(library)) {
     return Dart_Error("not a library");
   }
   if (!Dart_IsString8(url)) {
     return Dart_Error("url is not a string");
   }
   const char* url_string = NULL;
   Dart_Handle result = Dart_StringToCString(url, &url_string);
   if (Dart_IsError(result)) {
-    return Dart_Error("accessing url characters failed");
+    return result;
   }
 
   // If the URL starts with "dart:" then it is handled specially.
   bool is_dart_scheme_url = DartUtils::IsDartSchemeURL(url_string);
   if (tag == kCanonicalizeUrl) {
     if (is_dart_scheme_url) {
       return url;
     }
     return DartUtils::CanonicalizeURL(url_mapping, library, url_string);
   }
@@ skipping 27 matching lines @@
                                             Dart_Handle import_map) {
   if (!Dart_IsLibrary(library)) {
     return Dart_Error("not a library");
   }
   if (!Dart_IsString8(url)) {
     return Dart_Error("url is not a string");
   }
   const char* url_string = NULL;
   Dart_Handle result = Dart_StringToCString(url, &url_string);
   if (Dart_IsError(result)) {
-    return Dart_Error("accessing url characters failed");
+    return result;
   }
   // We only support canonicalization of "dart:".
   if (DartUtils::IsDartSchemeURL(url_string)) {
     if (tag == kCanonicalizeUrl) {
       return url;
     }
     // TODO(iposva): Make sure only the known libraries are being added.
     return Dart_True();
   }
   return Dart_Error("unexpected tag encountered %d", tag);
@@ skipping 115 matching lines @@
     exit(255);
   }
   // Now write the snapshot out to specified file and exit.
   WriteSnapshotFile(buffer, size);
   Dart_ExitScope();
 
   // Shutdown the isolate.
   Dart_ShutdownIsolate();
   return 0;
 }