Replace ResultProvider with 'aboutToComputeResult'.

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 c9604ef38f0e7b42ed6c5f8b7d1ba687e7aefcc7..88403fb59309d1a368dc6f227ce0392ef2d73eb2 100644
--- a/pkg/analyzer/lib/src/context/context.dart
+++ b/pkg/analyzer/lib/src/context/context.dart
@@ -485,6 +485,11 @@ class AnalysisContextImpl implements InternalAnalysisContext {
   }
 
   @override
+  bool aboutToComputeResult(CacheEntry entry, ResultDescriptor result) {
+    return false;
+  }
+
+  @override
   void addListener(AnalysisListener listener) {
     if (!_listeners.contains(listener)) {
       _listeners.add(listener);