Gardening: Add another Leak expectation for scroll customization

It's failing on Linux Leak. Probably r201736
https://codereview.chromium.org/1236913004 missed adding the
expectation.

Build: https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Leak/builds/13880
Leak log:
({"numberOfLiveActiveDOMObjects":[2,4],"numberOfLiveDocuments":[1,2],"numberOfLiveNodes":[4,36],"numberOfLiveResources":[0,2]})

BUG=410974
TBR=tdresser
NOTRY=true

Review URL: https://codereview.chromium.org/1326083003

git-svn-id: svn://svn.chromium.org/blink/trunk@201762 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/LeakExpectations

@@ -36,6 +36,7 @@ crbug.com/301515 fast/workers/worker-terminate.html [ Leak ]
 # FIXME: scroll customization leaks memory. See
 # codereview.chromium.org/1236913004/ for context.
 crbug.com/410974 virtual/scroll_customization/fast/scroll-behavior/scroll-customization/touch-scroll-customization.html [ Leak ]
+crbug.com/410974 virtual/scroll_customization/fast/scroll-behavior/scroll-customization/scrollstate-distribute-to-scroll-chain-descendant.html [ Leak ]
 
 # -----------------------------------------------------------------
 # Untriaged but known real leaks.