Restore AnalysisDeltaTest in Dart.

pkg/analyzer/lib/src/generated/engine.dart

Index: pkg/analyzer/lib/src/generated/engine.dart
diff --git a/pkg/analyzer/lib/src/generated/engine.dart b/pkg/analyzer/lib/src/generated/engine.dart
index 7a8f9332773687689bbf1a9a02ef91438be01a70..53e8644c7658aff34bd1093e15c96bfef1db28cb 100644
--- a/pkg/analyzer/lib/src/generated/engine.dart
+++ b/pkg/analyzer/lib/src/generated/engine.dart
@@ -5898,13 +5898,13 @@ class AnalysisDelta {
    *
    * @return a collection of the sources
    */
-  Iterable<Source> get addedSources {
+  List<Source> get addedSources {
     List<Source> result = new List<Source>();
-    for (MapEntry<Source, AnalysisLevel> entry in getMapEntrySet(_analysisMap)) {
-      if (entry.getValue() != AnalysisLevel.NONE) {
-        result.add(entry.getKey());
+    _analysisMap.forEach((Source source, AnalysisLevel level) {
+      if (level != AnalysisLevel.NONE) {
+        result.add(source);
       }
-    }
+    });
     return result;
   }