Update AnalysisServer to preserve DartC import prefixes

compiler/java/com/google/dart/compiler/parser/DartPrefixParser.java

Index: compiler/java/com/google/dart/compiler/parser/DartPrefixParser.java
===================================================================
--- compiler/java/com/google/dart/compiler/parser/DartPrefixParser.java	(revision 0)
+++ compiler/java/com/google/dart/compiler/parser/DartPrefixParser.java	(revision 0)
@@ -0,0 +1,43 @@
+/*
+ * Copyright 2012 Dart project authors.
+ * 
+ * Licensed under the Eclipse Public License v1.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ * 
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.google.dart.compiler.parser;
+
+import com.google.dart.compiler.ast.DartImportDirective;
+import com.google.dart.compiler.ast.DartStringLiteral;
+
+import java.util.Set;
+
+/**
+ * An extension of {@link DartParser} that updates the prefixes collection
+ */
+public class DartPrefixParser extends DartParser {
+
+  private final Set<String> prefixes;
+
+  public DartPrefixParser(ParserContext parserCtx, boolean isDietParse, Set<String> prefixes) {
+    super(parserCtx, isDietParse, prefixes);
+    this.prefixes = prefixes;
+  }
+  
+  @Override
+  protected DartImportDirective parseImportDirective() {
+    DartImportDirective directive = super.parseImportDirective();
+    DartStringLiteral prefix = directive.getPrefix();
+    if (prefix != null) {
+      prefixes.add(prefix.getValue());
+    }
+    return directive;
+  }
+}
+