[Sheriff] Mark profviz flaky on GC stress.

BUG=
TBR=hpayer@chromium.org

Review URL: https://codereview.chromium.org/149763002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18929 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

test/mjsunit/mjsunit.status

@@ -127,6 +127,9 @@
   'osr-elements-kind': [SKIP],
   'regress/regress-165637': [SKIP],
   'regress/regress-2249': [SKIP],
+
+  # TODO(hpayer): Investigate.
+  'tools/profviz': [PASS, FLAKY],
 }],  # 'gc_stress == True'
 
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