Update TestExpectations for scroll-parent-absolute.

The scrollbars appear not to draw content by default in some configs, so
we need to have different text dumps.

TBR=senorblanco@chromium.org
BUG=None

Review URL: https://codereview.chromium.org/348613002

git-svn-id: svn://svn.chromium.org/blink/trunk@176542 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/TestExpectations

@@ -130,6 +130,11 @@ crbug.com/330083 w3c/web-platform-tests/custom-elements/creating-and-passing-reg
 crbug.com/330083 w3c/web-platform-tests/shadow-dom/elements-and-dom-objects/shadowroot-object/shadowroot-attributes/test-014.html [ Timeout Failure ]
 crbug.com/330083 w3c/web-platform-tests/webrtc/simplecall.html [ Failure ]
 
+# Scrollbar differences.
+Bug(vollick) [ Mac ] virtual/softwarecompositing/overflow/scroll-parent-absolute.html [ NeedsRebaseline ]
+Bug(vollick) [ Mac ] virtual/gpu/compositedscrolling/overflow/scroll-parent-absolute.html [ NeedsRebaseline ]
+Bug(vollick) [ Mac ] compositing/overflow/scroll-parent-absolute.html [ NeedsRebaseline ]
+
 # Untriaged Aura-specific failure.
 crbug.com/229207 [ Win ] fast/forms/select/popup-closes-on-blur.html [ Failure ]