Make Sky's test_perf actually test performance

sky/tools/skypy/find_tests.py

Index: sky/tools/skypy/find_tests.py
diff --git a/sky/tools/skypy/find_tests.py b/sky/tools/skypy/find_tests.py
new file mode 100644
index 0000000000000000000000000000000000000000..7ea9367c120f1c8ac50c64f4c24a591c34402c02
--- /dev/null
+++ b/sky/tools/skypy/find_tests.py
@@ -0,0 +1,20 @@
+# Copyright 2014 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.
+
+import os
+
+
+IGNORED_DIRECTORIES = ['resources']
+TEST_EXTENSIONS = ['sky']
+
+
+def find_tests(directory):
+    for root, dirs, files in os.walk(directory):
+        for file_name in files:
+            extension = os.path.splitext(file_name)[1]
+            if extension.lstrip('.') in TEST_EXTENSIONS:
+                yield os.path.join(root, file_name)
+        for ignored_directory in IGNORED_DIRECTORIES:
+            if ignored_directory in dirs:
+                dirs.remove(ignored_directory)