fuchsia: Disable ServiceWorkerProviderHostTest in content_unittests

TBR: wez@chromium.org
Bug: 780508
Change-Id: Ib5325a3b0e7bb9fbbc9b1b8c9b18837b63dd0d95
Reviewed-on: https://chromium-review.googlesource.com/749247
Commit-Queue: Scott Graham <scottmg@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Reviewed-by: Scott Graham <scottmg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513182}

testing/buildbot/filters/fuchsia.content_unittests.filter

@@ -52,3 +52,6 @@
 
 # Flaky: https://crbug.com/777917.
 -LevelDBTransactionRangeTests/LevelDBTransactionRangeTest.*
+
+# Flaky: https://crbug.com/780508.
+-ServiceWorkerProviderHostTest.*