Mark inline-scope-variables.js flaky

Bug: 1150458
Change-Id: Id2720551fcfab68ea9ef9be8f97210fef89ed7ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2612869Reviewed-by: Tsuyoshi Horo <horo@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841012}

third_party/blink/web_tests/TestExpectations

@@ -5832,6 +5832,7 @@ crbug.com/1152088 [ Mac10.13 Debug ] fast/dom/cssTarget-crash.html [ Pass Timeou
 crbug.com/1149734 http/tests/devtools/sources/source-frame-toolbar-items.js [ Pass Failure ]
 crbug.com/1149734 http/tests/devtools/sources/debugger-frameworks/frameworks-sourcemap.js [ Pass Failure ]
 crbug.com/1149734 http/tests/devtools/sources/debugger-ui/continue-to-location-markers.js [ Pass Failure ]
+crbug.com/1149734 http/tests/devtools/sources/debugger-ui/inline-scope-variables.js [ Pass Failure ]
 
 #Sheriff 2020-11-24
 crbug.com/1152496 [ Win ] virtual/oopr-canvas2d/fast/canvas/canvas-composite-shadow.html [ Pass Timeout ]