Disable loading.desktop/Walgreens_* stories on all platforms

TBR=kouhei@chromium.org, ksakamoto@chromium.org
NOTRY=true

Bug: 892191
Change-Id: Ia164f2364d68118ee4538377c6f4e193034f9452
Reviewed-on: https://chromium-review.googlesource.com/c/1266890Reviewed-by: Ned Nguyen <nednguyen@google.com>
Commit-Queue: Ned Nguyen <nednguyen@google.com>
Cr-Commit-Position: refs/heads/master@{#597429}

tools/perf/expectations.config

@@ -73,6 +73,8 @@ crbug.com/876636 [ ChromeOS ] loading.desktop/AllRecipes_cold [ Skip ]
 crbug.com/876636 [ ChromeOS ] loading.desktop/AllRecipes_warm [ Skip ]
 crbug.com/879833 [ Mac_10.12 ] loading.desktop/AllRecipes_cold [ Skip ]
 crbug.com/879833 [ Win ] loading.desktop/AllRecipes_cold [ Skip ]
+crbug.com/879833 [ All ] loading.desktop/Walgreens_cold [ Skip ]
+crbug.com/879833 [ All ] loading.desktop/Walgreens_warm [ Skip ]
 
 # Benchmark: loading.mobile
 crbug.com/656861 [ All ] loading.mobile/G1 [ Skip ]