Disable flaky mobile.loading test on Nexus 6 Webview

TBR=ksakamoto@chromium.org
NOTRY=true

Bug: 676612
Change-Id: Ia70720a2d00c4c7560736db33d8bbe7b418a87e5
Reviewed-on: https://chromium-review.googlesource.com/1170593Reviewed-by: Ned Nguyen <nednguyen@google.com>
Commit-Queue: Ned Nguyen <nednguyen@google.com>
Cr-Commit-Position: refs/heads/master@{#582170}

tools/perf/expectations.config

@@ -114,6 +114,12 @@ crbug.com/867103 [ Nexus5X_Webview ] loading.mobile/FlipBoard_warm_3g [ Skip ]
 crbug.com/871421 [ Android_One ] loading.mobile/Dramaq_3g [ Skip ]
 crbug.com/873032 [ Android_Webview ] loading.mobile/GoogleRedirectToGoogleJapan_3g [ Skip ]
 crbug.com/873033 [ Android_but_not_webview ] loading.mobile/FlipKart_warm_3g [ Skip ]
+crbug.com/676612 [ Nexus6_Webview ] loading.mobile/FlipBoard_cold_3g [ Skip ]
+crbug.com/676612 [ Nexus6_Webview ] loading.mobile/FlipBoard_warm_3g [ Skip ]
+crbug.com/676612 [ Nexus6_Webview ] loading.mobile/TribunNews_3g [ Skip ]
+crbug.com/676612 [ Nexus6_Webview ] loading.mobile/FlipKart_warm_3g [ Skip ]
+crbug.com/676612 [ Nexus6_Webview ] loading.mobile/OLX_3g [ Skip ]
+crbug.com/676612 [ Nexus6_Webview ] loading.mobile/Youtube_3g [ Skip ]
 
 # Benchmark: memory.long_running_idle_gmail_tbmv2
 crbug.com/611167 [ Android_Svelte ] memory.long_running_idle_gmail_tbmv2/* [ Skip ]