Mark external/wpt/svg/animations/slider-switch.html as flaky

Tbr: schenney@chromium.org
Bug: 1013736
Change-Id: I360252f5459be10231bf1edf291f45dc46c9f705
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1857325Reviewed-by: Fredrik Söderquist <fs@opera.com>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#705484}

third_party/blink/web_tests/TestExpectations

@@ -215,6 +215,8 @@ crbug.com/730267 virtual/gpu-rasterization/images/yuv-decode-eligible/color-prof
 crbug.com/730267 virtual/gpu-rasterization-disable-yuv/images/yuv-decode-eligible/color-profile-layer.html [ Pass Timeout Failure ]
 crbug.com/730267 virtual/gpu-rasterization-disable-yuv/images/yuv-decode-eligible/color-profile-layer-filter.html [ Pass Timeout Failure ]
 
+crbug.com/1013736 external/wpt/svg/animations/slider-switch.html [ Pass Failure ]
+
 # Flaky virtual/threaded/fast/scrolling tests
 crbug.com/841567 virtual/threaded/fast/scrolling/absolute-position-behind-scrollbar.html [ Failure Pass ]
 crbug.com/841567 virtual/threaded/fast/scrolling/fixed-position-behind-scrollbar.html [ Failure Pass ]