Fix how JsChecker::GetBoolImpl enforces boolean result

chrome/browser/chromeos/login/test/js_checker.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/chromeos/login/test/js_checker.h"
 
 #include "base/strings/utf_string_conversions.h"
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/test/browser_test_utils.h"
@@ skipping 68 matching lines @@
   EXPECT_EQ(GetString(expression), result) << expression;
 }
 
 void JSChecker::ExpectNE(const std::string& expression,
                          const std::string& result) {
   EXPECT_NE(GetString(expression), result) << expression;
 }
 
 void JSChecker::GetBoolImpl(const std::string& expression, bool* result) {
   CHECK(web_contents_);
-  ASSERT_TRUE(content::ExecuteScriptAndExtractBool(web_contents_,
-                                                   "!!" + WrapSend(expression),
-                                                   result));
+  ASSERT_TRUE(content::ExecuteScriptAndExtractBool(
+      web_contents_, WrapSend("!!(" + expression + ")"), result));
 }
 
 void JSChecker::GetIntImpl(const std::string& expression, int* result) {
   CHECK(web_contents_);
   ASSERT_TRUE(content::ExecuteScriptAndExtractInt(web_contents_,
                                                   WrapSend(expression),
                                                   result));
 }
 
 void JSChecker::GetStringImpl(const std::string& expression,
                               std::string* result) {
   CHECK(web_contents_);
   ASSERT_TRUE(content::ExecuteScriptAndExtractString(web_contents_,
                                                      WrapSend(expression),
                                                      result));
 }
 
 }  // namespace test
 }  // namespace chromeos