Issue 27358. Reset AnalysisContext 'sourceFactory' and 'typeSystem' on analysis options change.

pkg/analysis_server/lib/src/context_manager.dart

Index: pkg/analysis_server/lib/src/context_manager.dart
diff --git a/pkg/analysis_server/lib/src/context_manager.dart b/pkg/analysis_server/lib/src/context_manager.dart
index 7d567a9d8fd15f1910e086e3a733f3826e0949f6..8e9787a3b0ef1972d51e9a7201b68887d39c7c68 100644
--- a/pkg/analysis_server/lib/src/context_manager.dart
+++ b/pkg/analysis_server/lib/src/context_manager.dart
@@ -891,7 +891,8 @@ class ContextManagerImpl implements ContextManager {
         Map<String, Object> options = readOptions(info.folder);
         processOptionsForContext(info, options,
             optionsRemoved: changeType == ChangeType.REMOVE);
-        analysisContext.invalidateCachedResults();
+        analysisContext.sourceFactory = _createSourceFactory(
+            analysisContext, analysisContext.analysisOptions, info.folder);
         callbacks.applyChangesToContext(info.folder, new ChangeSet());
       }
     }