Fix for duplicate priority sources.

pkg/analysis_server/lib/src/analysis_server.dart

 // Copyright (c) 2014, 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 analysis.server;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:core' hide Resource;
 import 'dart:math' show max;
@@ skipping 1067 matching lines @@
           }
         }
       }
       // Fill the source map.
       bool contextFound = false;
       if (preferredContext != null) {
         sourceMap.putIfAbsent(preferredContext, () => <Source>[]).add(source);
         contextFound = true;
       }
       for (AnalysisContext context in folderMap.values) {
-        if (context.getKindOf(source) != SourceKind.UNKNOWN) {
+        if (context != preferredContext &&
+            context.getKindOf(source) != SourceKind.UNKNOWN) {
           sourceMap.putIfAbsent(context, () => <Source>[]).add(source);
           contextFound = true;
         }
       }
       if (firstSource == null) {
         firstSource = source;
       }
       if (!contextFound) {
         unanalyzed.add(file);
       }
@@ skipping 506 matching lines @@
   /**
    * The [PerformanceTag] for time spent in server request handlers.
    */
   static PerformanceTag serverRequests = new PerformanceTag('serverRequests');
 
   /**
    * The [PerformanceTag] for time spent in split store microtasks.
    */
   static PerformanceTag splitStore = new PerformanceTag('splitStore');
 }