Mark feature-policy-image-policies-with-border-radius.html flaky

Bug: 924954
Tbr: ekaramad@chromium.org
Change-Id: I6e85f34064d2f251dd38731cb37d7c512014d9c2
Reviewed-on: https://chromium-review.googlesource.com/c/1433619Reviewed-by: Oskar Sundbom <ossu@chromium.org>
Commit-Queue: Oskar Sundbom <ossu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625636}

third_party/blink/web_tests/TestExpectations

@@ -5972,3 +5972,6 @@ crbug.com/v8/8319 external/wpt/wasm/jsapi/memory/grow.any.worker.html [ Pass Fai
 # Sheriff 2019-01-22
 # Likely needs a rebaseline
 crbug.com/921242 [ Mac ] fast/overflow/clip-rects-fixed-ancestor.html [ Failure ]
+
+# Sheriff 2019-01-24
+crbug.com/924954 http/tests/images/feature-policy-image-policies-with-border-radius.html [ Pass Failure ]