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

pkg/analyzer/lib/src/context/context.dart

Index: pkg/analyzer/lib/src/context/context.dart
diff --git a/pkg/analyzer/lib/src/context/context.dart b/pkg/analyzer/lib/src/context/context.dart
index 3b6846fb6b3db9ca99dbbc5ccf78ac4033f9c6cc..f56c12cc3c1a86f86c224ff8933c59517ea8461f 100644
--- a/pkg/analyzer/lib/src/context/context.dart
+++ b/pkg/analyzer/lib/src/context/context.dart
@@ -329,6 +329,9 @@ class AnalysisContextImpl implements InternalAnalysisContext {
     this._options.incrementalValidation = options.incrementalValidation;
     this._options.lint = options.lint;
     this._options.preserveComments = options.preserveComments;
+    if (this._options.strongMode != options.strongMode) {
+      _typeSystem = null;
+    }
     this._options.strongMode = options.strongMode;
     this._options.trackCacheDependencies = options.trackCacheDependencies;
     this._options.finerGrainedInvalidation = options.finerGrainedInvalidation;