Reenable loading.mobile on Nexus6 WebView

Capacity issue on Nexus6 Webview has been resolved, so this may be ok to reenable
the benchmarks on this platform now

TBR=ksakamoto@chromium.org
NOTRY=true

Bug: 676612
Change-Id: I8f6a93767d47f94ba66a8a9df43b8d3a0b03b951
Reviewed-on: https://chromium-review.googlesource.com/1170422Reviewed-by: Ned Nguyen <nednguyen@google.com>
Commit-Queue: Ned Nguyen <nednguyen@google.com>
Cr-Commit-Position: refs/heads/master@{#582039}

tools/perf/expectations.config

@@ -75,7 +75,6 @@ crbug.com/752611 [ Linux ] loading.desktop/uol.com.br_warm [ Skip ]
 crbug.com/867836 [ All ] loading.desktop/Elmundo_warm [ Skip ]
 
 # Benchmark: loading.mobile
-crbug.com/676612 [ Nexus6_Webview ] loading.mobile/* [ Skip ]
 crbug.com/776092 [ Android_One ] loading.mobile/GoogleRedirectToGoogleJapan [ Skip ]
 crbug.com/656861 [ All ] loading.mobile/G1 [ Skip ]
 crbug.com/857108 [ Nexus_5 ] loading.mobile/G1_3g [ Skip ]