Add 'containingClassDescription' to HoverInformation.

pkg/analysis_server/lib/src/computer/computer_hover.dart

Index: pkg/analysis_server/lib/src/computer/computer_hover.dart
diff --git a/pkg/analysis_server/lib/src/computer/computer_hover.dart b/pkg/analysis_server/lib/src/computer/computer_hover.dart
index 9cc2f41ec2be66d45c3b4268d5a019897c5f7a50..aad7ca3b0eab69d3a36893541ac285230c818735 100644
--- a/pkg/analysis_server/lib/src/computer/computer_hover.dart
+++ b/pkg/analysis_server/lib/src/computer/computer_hover.dart
@@ -95,7 +95,13 @@ class DartUnitHoverComputer {
         // description
         hover.elementDescription = element.toString();
         hover.elementKind = element.kind.displayName;
-        // library
+        // containing class
+        ClassElement containingClass =
+            element.getAncestor((e) => e is ClassElement);
+        if (containingClass != null) {
+          hover.containingClassDescription = containingClass.toString();
+        }
+        // containing library
         LibraryElement library = element.library;
         if (library != null) {
           hover.containingLibraryName = library.name;