Fix incorrect desugaring of cascades.

tests/language/cascade_2_test.dart

 // Copyright (c) 2012, 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.
 
-// Test cascades, issue 7665.
+// Test cascades, issues 7494 (vm), 7689 (dart2js).
 
 main() {
   var a = new Element(null);
   Expect.equals(1, a.path0.length);
   Expect.equals(a, a.path0[0]);
 
-  Expect.equals(1, a.path1.length);  // 2 instead of 1
+  // Issue 7693: e0 ? e1 : e2..f() parses as (e0 ? e1 : e2)..f().
+  Expect.equals(2, a.path1.length);
   Expect.equals(a, a.path1[0]);
+  Expect.equals(a, a.path1[1]);
 
   Expect.equals(1, a.path2.length);  // NPE.
 
   var b = new Element(a);
   Expect.equals(2, b.path0.length);
   Expect.equals(a, b.path0[0]);
   Expect.equals(b, b.path0[1]);
 
-  Expect.equals(2, b.path1.length);  // 3 instead of 2.
+  Expect.equals(3, b.path1.length);
   Expect.equals(a, b.path1[0]);
-  Expect.equals(b, b.path1[1]);
+  Expect.equals(a, b.path1[1]);
+  Expect.equals(b, b.path1[2]);
 
   Expect.equals(2, b.path2.length);  // NPE.
 }
 
 
 class Element {
   final Element parent;
 
   Element(this.parent);
 
   List<Element> get path0 {
     if (parent == null) {
       return <Element>[this];
     } else {
       return parent.path0..add(this);
     }
   }
 
   List<Element> get path1 {
     return (parent == null) ? <Element>[this] : parent.path1..add(this);
   }
 
   List<Element> get path2 {
     return (parent == null) ? <Element>[this] : (parent.path2..add(this));
   }
 }