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

Review URL: http://codereview.chromium.org/8510065

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@110999 0039d316-1c4b-4281-b951-d872f2087c98

chrome/test/ui/ui_layout_test.cc

@@ -149,6 +149,7 @@ void UILayoutTest::InitializeForLayoutTest(const FilePath& test_parent_dir,
   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_));
 }