Add a test of summaries that uses strong mode.

pkg/analyzer/test/src/summary/summary_common.dart

 // Copyright (c) 2015, 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 analyzer.test.src.summary.summary_common;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
@@ skipping 2543 matching lines @@
     expect(executable.isConst, false);
     expect(executable.isFactory, false);
     expect(executable.isStatic, false);
     expect(executable.parameters, hasLength(1));
     checkTypeRef(executable.returnType, null, null, 'C');
     expect(executable.typeParameters, isEmpty);
     expect(executable.isExternal, false);
   }
 
   test_executable_operator_equal() {
-    UnlinkedExecutable executable =
-        serializeClassText('class C { bool operator==(C other) => false; }')
-            .executables[0];
+    UnlinkedExecutable executable = serializeClassText(
+        'class C { bool operator==(Object other) => false; }').executables[0];
     expect(executable.name, '==');
   }
 
   test_executable_operator_external() {
     UnlinkedExecutable executable =
         serializeClassText('class C { external C operator+(C c); }')
             .executables[0];
     expect(executable.isExternal, true);
   }
 
@@ skipping 1649 matching lines @@
     expect(constExpr.operations, operators);
     expect(constExpr.ints, ints);
     expect(constExpr.doubles, doubles);
     expect(constExpr.strings, strings);
     expect(constExpr.references, hasLength(referenceValidators.length));
     for (int i = 0; i < referenceValidators.length; i++) {
       referenceValidators[i](constExpr.references[i]);
     }
   }
 }