Fix test.py and tests to use an explicit --packages flag.

tools/testing/dart/test_options.dart

 // Copyright (c) 2013, 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.
 
 library test_options_parser;
 
 import "dart:io";
 import "drt_updater.dart";
 import "test_suite.dart";
 import "path.dart";
@@ skipping 790 matching lines @@
         if (selectorMap.containsKey(suite)) {
           print("Error: '$suite/$pattern'.  Only one test selection"
               " pattern is allowed to start with '$suite/'");
           exit(1);
         }
         selectorMap[suite] = new RegExp(pattern);
       }
       configuration['selectors'] = selectorMap;
     }
 
+    // Put observatory_ui in a configuration with its own packages override.
+    // Only one value in the configuration map is mutable:
+    selectors = configuration['selectors'];
+    if (selectors.containsKey('observatory_ui')) {
+      if (selectors.length == 1) {
+        configuration['packages'] = TestUtils.dartDirUri
+          .resolve('runtime/observatory/.packages').toFilePath();
+      } else {
+        // Make a new configuration whose selectors map only contains
+        // observatory_ui, and remove the key from the original selectors.
+        // The only mutable value in the map is the selectors, so a
+        // shallow copy is safe.
+        var observatoryConfiguration = new Map.from(configuration);
+        observatoryConfiguration['selectors'] =
+          {'observatory_ui': selectors['observatory_ui']};
+        selectors.remove('observatory_ui');
+
+        // Set the packages flag.
+        observatoryConfiguration['packages'] = TestUtils.dartDirUri
+          .resolve('runtime/observatory/.packages').toFilePath();
+
+        // Return the expansions of both configurations. Neither will reach
+        // this line in the recursive call to _expandConfigurations.
+        return _expandConfigurations(configuration)
+          ..addAll(_expandConfigurations(observatoryConfiguration));
+      }
+    }
+    // Set the default package spec explicitly.
+    if (configuration['package_root'] == null &&
+        configuration['packages'] == null) {
+      configuration['packages'] =
+        TestUtils.dartDirUri.resolve('.packages').toFilePath();     
+    }
+    
     // Expand the architectures.
     if (configuration['arch'].contains(',')) {
       return _expandHelper('arch', configuration);
     }
 
     // Expand modes.
     if (configuration['mode'].contains(',')) {
       return _expandHelper('mode', configuration);
     }
 
@@ skipping 104 matching lines @@
       if (option.keys.contains(name)) {
         return option;
       }
     }
     print('Unknown test option $name');
     exit(1);
   }
 
   List<_TestOptionSpecification> _options;
 }