Fix orphaned wpt -expected.txt file deletion logic.

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/base.py

Index: third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/base.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/base.py b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/base.py
index 98c179c04c9969e74ab2a1b6b76b11021bf23f46..e301ee4c29c156a680078f33b1e544ee7988f0fd 100644
--- a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/base.py
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/base.py
@@ -661,7 +661,7 @@ class Port(object):
         # Try to find -expected.* or -expected-mismatch.* in the same directory.
         reftest_list = []
         for expectation, prefix in (('==', ''), ('!=', '-mismatch')):
-            for extension in Port._supported_file_extensions:
+            for extension in Port.supported_file_extensions:
                 path = self.expected_filename(test_name, prefix + extension)
                 if self._filesystem.exists(path):
                     reftest_list.append((expectation, path))
@@ -696,10 +696,6 @@ class Port(object):
                                 skipped_directories, functools.partial(Port.is_test_file, self), self.test_key)
         return self._convert_wpt_file_paths_to_url_paths([self.relative_test_filename(f) for f in files])
 
-    # When collecting test cases, we include any file with these extensions.
-    _supported_file_extensions = set(['.html', '.xml', '.xhtml', '.xht', '.pl',
-                                      '.htm', '.php', '.svg', '.mht', '.pdf'])
-
     @staticmethod
     # If any changes are made here be sure to update the isUsedInReftest method in old-run-webkit-tests as well.
     def is_reference_html_file(filesystem, dirname, filename):
@@ -711,11 +707,17 @@ class Port(object):
                 return True
         return False
 
+    # When collecting test cases, we include any file with these extensions.
+    supported_file_extensions = set([
+        '.html', '.xml', '.xhtml', '.xht', '.pl',
+        '.htm', '.php', '.svg', '.mht', '.pdf',
+    ])
+
     @staticmethod
     def _has_supported_extension(filesystem, filename):
         """Returns True if filename is one of the file extensions we want to run a test on."""
         extension = filesystem.splitext(filename)[1]
-        return extension in Port._supported_file_extensions
+        return extension in Port.supported_file_extensions
 
     def is_test_file(self, filesystem, dirname, filename):
         match = re.search(r'[/\\]external[/\\]wpt([/\\].*)?$', dirname)