Don't run main if library failed to import

Source/bindings/dart/DartApplicationLoader.cpp

 // Copyright (c) 2009, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
@@ skipping 83 matching lines @@
         // DartDOMData::current()->applicationLoader() may be 0 at this point.
         return DartUtilities::canonicalizeUrl(library, urlHandle, url);
     }
 
     ASSERT(DartDOMData::current()->applicationLoader());
     return DartDOMData::current()->applicationLoader()->libraryTagHandler(tag, library, urlHandle, url);
 }
 
 Dart_Handle DartApplicationLoader::libraryTagHandler(Dart_LibraryTag tag, Dart_Handle library, Dart_Handle urlHandle, String url)
 {
-    ASSERT(m_asyncLoader->contains(url));
+    if (!m_asyncLoader->contains(url)) {
+        scriptLoadError(url);
+        return Dart_NewBoolean(false);
+    }
+
     const String& source = m_asyncLoader->get(url);
 
     Dart_Handle import;
     if (tag == Dart_kImportTag) {
         import = Dart_LoadLibrary(DartUtilities::stringToDartString(url), DartUtilities::convertSourceString(source));
     } else if (tag == Dart_kSourceTag) {
         import = Dart_LoadSource(library, DartUtilities::stringToDartString(url), DartUtilities::convertSourceString(source));
     } else {
         ASSERT_NOT_REACHED();
+        m_scriptHasError = true;
         DartUtilities::reportProblem(m_originDocument, "Invalid import tag");
         return Dart_NewBoolean(false);
     }
 
     if (Dart_IsError(import)) {
         reportDartError(import);
         return Dart_NewBoolean(false);
     }
 
     return Dart_NewBoolean(true);
@@ skipping 129 matching lines @@
 
 Dart_Handle DartApplicationLoader::topLevelLibrary()
 {
     Dart_Handle library = Dart_LookupLibrary(DartUtilities::stringToDartString(m_libraryUrl));
     ASSERT(!Dart_IsError(library));
     return library;
 }
 
 void DartApplicationLoader::scriptLoadError(String failedUrl)
 {
+    m_scriptHasError = true;
     // FIXME: try to dig out line number, -1 for now.
     if (failedUrl.startsWith(String("dart:"))) {
         m_originDocument->logExceptionToConsole(String("The built-in library '") + failedUrl + String("' is not available on Dartium."), m_libraryUrl, -1, 0, 0);
     } else {
         m_originDocument->logExceptionToConsole(String("Failed to load a file ") + failedUrl, m_libraryUrl, -1, 0, 0);
     }
     m_errorEventDispatcher->dispatchErrorEvent();
 }
 
 }