Make credential_path a page attribute instead of page_set attribute.

tools/telemetry/telemetry/util/classes.py

Index: tools/telemetry/telemetry/util/classes.py
diff --git a/tools/telemetry/telemetry/util/classes.py b/tools/telemetry/telemetry/util/classes.py
new file mode 100644
index 0000000000000000000000000000000000000000..c8556b113f3a1f851bc29a2c7fb3e5650dc9a13b
--- /dev/null
+++ b/tools/telemetry/telemetry/util/classes.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 inspect
+
+def IsDirectlyConstructable(cls):
+  assert inspect.isclass(cls)
+  # Case class A: pass
+  if not hasattr(cls, '__init__'):
+    return True
+  # Case class A(object): pass
+  if cls.__init__ is object.__init__:
+    return True
+  # Case class has __init__ method which is not object.__init__.
+  args, _1, _2, defaults = inspect.getargspec(cls.__init__)
+  if defaults is None:
+    defaults = []
+  return ('self' in args and
+          len(args) == len(defaults) + 1)