local cascade suggestion fix and move towards common tests

pkg/analysis_server/lib/src/services/completion/local_computer.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library services.completion.computer.dart.local;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/protocol.dart' as protocol show Element, ElementKind;
 import 'package:analysis_server/src/protocol.dart' hide Element, ElementKind;
@@ skipping 186 matching lines @@
     _addParamListSuggestions(node.parameters);
     visitNode(node);
   }
 
   @override
   visitNode(AstNode node) {
     node.parent.accept(this);
   }
 
   @override
+  visitCascadeExpression(CascadeExpression node) {
+    Expression target = node.target;
+    // This computer handles the expression
+    // while InvocationComputer handles the cascade selector
+    if (target != null && request.offset <= target.end) {
+      visitNode(node);
+    }
+  }
+
+  @override
   visitVariableDeclaration(VariableDeclaration node) {
     // Do not add suggestions if editing the name in a var declaration
     SimpleIdentifier name = node.name;
     if (name == null ||
         name.offset < request.offset ||
         request.offset > name.end) {
       visitNode(node);
     }
   }
 
@@ skipping 216 matching lines @@
     if (name == null || name.length <= 0) {
       return DYNAMIC;
     }
     TypeArgumentList typeArgs = type.typeArguments;
     if (typeArgs != null) {
       //TODO (danrubel) include type arguments
     }
     return name;
   }
 }