Context invalidation on option changes (Implements #24574).

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 1aaa6911fac75e27c9f0d73fd8a892b8f0219587..dd2893f8fedc004f8b5f916bade9924fdcaa814a 100644
--- a/pkg/analyzer/lib/src/context/context.dart
+++ b/pkg/analyzer/lib/src/context/context.dart
@@ -415,6 +415,13 @@ class AnalysisContextImpl implements InternalAnalysisContext {
     }
   }
 
+  /**
+   * Invalidate analysis cache.
+   */
+  void invalidateCachedResults() {
+    _cache = createCacheFromSourceFactory(_sourceFactory);
+  }
+
   @override
   List<Source> get sources {
     return _cache.sources.toList();