When user renames 'prefix' in 'prefix.Class' she actually wants to rename ImportElement.

pkg/analysis_server/lib/src/analysis_server.dart

Index: pkg/analysis_server/lib/src/analysis_server.dart
diff --git a/pkg/analysis_server/lib/src/analysis_server.dart b/pkg/analysis_server/lib/src/analysis_server.dart
index b56a727f3fb0b8cba59c5dfa8a592841eefab6d5..43aef8a51fc47892d8b8d981bb5fdab5347abd99 100644
--- a/pkg/analysis_server/lib/src/analysis_server.dart
+++ b/pkg/analysis_server/lib/src/analysis_server.dart
@@ -30,6 +30,7 @@ import 'package:analysis_server/src/services/correction/change.dart';
 import 'package:analysis_server/src/services/index/index.dart';
 import 'package:analysis_server/src/services/search/search_engine.dart';
 import 'package:analyzer/src/generated/element.dart';
+import 'package:analysis_server/src/services/correction/namespace.dart';
 
 
 class ServerContextManager extends ContextManager {
@@ -681,6 +682,9 @@ class AnalysisServer {
     for (CompilationUnit unit in units) {
       AstNode node = new NodeLocator.con1(offset).searchWithin(unit);
       Element element = ElementLocator.locateWithOffset(node, offset);
+      if (node is SimpleIdentifier && element is PrefixElement) {
+        element = getImportElement(node);
+      }
       if (element != null) {
         elements.add(element);
       }