Make credential_path a page attribute instead of page_set attribute.

tools/telemetry/telemetry/unittest/page_set_smoke_test.py

Index: tools/telemetry/telemetry/unittest/page_set_smoke_test.py
diff --git a/tools/telemetry/telemetry/unittest/page_set_smoke_test.py b/tools/telemetry/telemetry/unittest/page_set_smoke_test.py
index bfe86e08f6bc6ba9f0dd2d654128c47fe8af5403..274161b9065833acb5db2fc538d16c1cd8c0fe22 100644
--- a/tools/telemetry/telemetry/unittest/page_set_smoke_test.py
+++ b/tools/telemetry/telemetry/unittest/page_set_smoke_test.py
@@ -10,6 +10,7 @@ from telemetry.core import browser_credentials
 from telemetry.core import discover
 from telemetry.page import page_set as page_set_module
 from telemetry.page import page_set_archive_info
+from telemetry.util import classes
 
 
 class PageSetSmokeTest(unittest.TestCase):
@@ -40,11 +41,11 @@ class PageSetSmokeTest(unittest.TestCase):
 
   def CheckCredentials(self, page_set):
     """Verify that all pages in page_set use proper credentials"""
-    credentials = browser_credentials.BrowserCredentials()
-    if page_set.credentials_path:
-      credentials.credentials_path = (
-          os.path.join(page_set.base_dir, page_set.credentials_path))
     for page in page_set.pages:
+      credentials = browser_credentials.BrowserCredentials()
+      if page.credentials_path:
+        credentials.credentials_path = (
+            os.path.join(page.base_dir, page.credentials_path))
       fail_message = ('page %s of %s has invalid credentials %s' %
                       (page.url, page_set.file_path, page.credentials))
       if page.credentials:
@@ -105,10 +106,11 @@ class PageSetSmokeTest(unittest.TestCase):
     page_sets = discover.DiscoverClasses(page_sets_dir, top_level_dir,
                                          page_set_module.PageSet).values()
     for page_set_class in page_sets:
-      try:
-        page_set = page_set_class()
-      except TypeError:
+      if not classes.IsDirectlyConstructable(page_set_class):
+        # We can't test page sets that aren't directly constructable since we
+        # don't know what arguments to put for the constructor.
         continue
+      page_set = page_set_class()
       logging.info('Testing %s', page_set.file_path)
       self.CheckArchive(page_set)
       self.CheckCredentials(page_set)