Only inject one copy of the javascript based 'LayoutTestController' instance.

chrome/test/ui/ui_layout_test.cc

 // Copyright (c) 2011 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/test/ui/ui_layout_test.h"
 
 #include "base/file_util.h"
 #include "base/path_service.h"
 #include "base/string_number_conversions.h"
 #include "base/string_util.h"
@@ skipping 131 matching lines @@
         new_parent_resource_path.AppendASCII("resources");
     ASSERT_TRUE(file_util::CopyDirectory(
         parent_resource_path, new_parent_resource_path, true));
   }
 
   // Reads the layout test controller simulation script.
   FilePath path;
   PathService::Get(chrome::DIR_TEST_DATA, &path);
   path = path.AppendASCII("layout_tests");
   path = path.AppendASCII("layout_test_controller.html");
+  layout_test_controller_.clear();
   ASSERT_TRUE(file_util::ReadFileToString(path, &layout_test_controller_));
 }
 
 void UILayoutTest::AddResourceForLayoutTest(const FilePath& parent_dir,
                                             const FilePath& resource_name) {
   FilePath source = GetLayoutTestRoot();
   source = source.Append(parent_dir);
   source = source.Append(resource_name);
 
   ASSERT_TRUE(file_util::PathExists(source));
@@ skipping 113 matching lines @@
                                       std::string* expected_result_value) {
   FilePath expected_result_path(result_dir_path);
   expected_result_path = expected_result_path.AppendASCII(test_case_file_name);
   expected_result_path = expected_result_path.InsertBeforeExtension(
       FILE_PATH_LITERAL("-expected"));
   expected_result_path =
       expected_result_path.ReplaceExtension(FILE_PATH_LITERAL("txt"));
   return file_util::ReadFileToString(expected_result_path,
                                      expected_result_value);
 }