Rework recent changes to LineInfo to be backward compatible.

pkg/analysis_server/lib/src/status/get_handler.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.src.status.get_handler;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:io';
@@ skipping 673 matching lines @@
                 } else {
                   String typeName = target.runtimeType.toString();
                   incrementCount(typeCounts, typeName);
                 }
               }
             }
 
             int lineCount(Set<Source> sources, bool explicit) {
               return sources.fold(0, (int previousTotal, Source source) {
                 LineInfo lineInfo = context.getLineInfo(source);
-                if (lineInfo == null) {
+                if (lineInfo is LineInfoWithCount) {
+                  if (explicit) {
+                    explicitLineInfoCount++;
+                  } else {
+                    implicitLineInfoCount++;
+                  }
+                  return previousTotal + lineInfo.lineCount;
+                } else {
                   return previousTotal;
                 }
-                if (explicit) {
-                  explicitLineInfoCount++;
-                } else {
-                  implicitLineInfoCount++;
-                }
-                return previousTotal + lineInfo.lineCount;
               });
             }
             explicitSourceCount += explicitSources.length;
             explicitLineCount += lineCount(explicitSources, true);
             implicitSourceCount += implicitSources.length;
             implicitLineCount += lineCount(implicitSources, false);
           });
           List<String> sourceTypeNames = sourceTypeCounts.keys.toList();
           sourceTypeNames.sort();
           List<String> typeNames = typeCounts.keys.toList();
@@ skipping 1755 matching lines @@
    */
   static String makeLink(
       String path, Map<String, String> params, String innerHtml,
       [bool hasError = false]) {
     Uri uri = new Uri(path: path, queryParameters: params);
     String href = HTML_ESCAPE.convert(uri.toString());
     String classAttribute = hasError ? ' class="error"' : '';
     return '<a href="$href"$classAttribute>$innerHtml</a>';
   }
 }