Disable loading.mobile/Dramaq_3g on A1

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

Bug: 871421
Change-Id: Id7806641d8827f7036ce213296a42e8b8f801e3a
Reviewed-on: https://chromium-review.googlesource.com/1164165Reviewed-by: Charlie Andrews <charliea@chromium.org>
Commit-Queue: Charlie Andrews <charliea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580976}

tools/perf/expectations.config

@@ -112,6 +112,7 @@ crbug.com/859597 [ Nexus_5X ] loading.mobile/QQNews_3g [ Skip ]
 crbug.com/859597 [ Nexus_5X ] loading.mobile/Youtube_3g [ Skip ]
 crbug.com/859597 [ Nexus5X_Webview ] loading.mobile/GoogleBrazil_3g [ Skip ]
 crbug.com/867103 [ Nexus5X_Webview ] loading.mobile/FlipBoard_warm_3g [ Skip ]
+crbug.com/871421 [ Android_One ] loading.mobile/Dramaq_3g [ Skip ]
 
 # Benchmark: memory.long_running_idle_gmail_tbmv2
 crbug.com/611167 [ Android_Svelte ] memory.long_running_idle_gmail_tbmv2/* [ Skip ]