More fixes for webpages_playback

BUG=skia:5843
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2409753002

Review-Url: https://codereview.chromium.org/2409753002
diff --git a/tools/skp/webpages_playback.py b/tools/skp/webpages_playback.py
index 67bb198..1320a86 100644
--- a/tools/skp/webpages_playback.py
+++ b/tools/skp/webpages_playback.py
@@ -102,7 +102,7 @@
 RETRY_RUN_MEASUREMENT_COUNT = 5
 
 # Location of the credentials.json file in Google Storage.
-CREDENTIALS_GS_PATH = '/playback/credentials/credentials.json'
+CREDENTIALS_GS_PATH = 'playback/credentials/credentials.json'
 
 X11_DISPLAY = os.getenv('DISPLAY', ':0')
 
@@ -480,7 +480,7 @@
           'gsutil', 'ls', '/'.join((self._url, name))])
     except subprocess.CalledProcessError:
       return False
-    if len(output.splitlines) != 1:
+    if len(output.splitlines()) != 1:
       return False
     return True