Schedule WebKit Linux Trusty ASAN/MSAN/Leak.

TBR=martiniss@chromium.org

Bug: 790286,790294,790309
Change-Id: I507b1c98aa2aca9e723db051cc59c0b51ebfb5ad
Reviewed-on: https://chromium-review.googlesource.com/c/1331614Reviewed-by: Jao-ke Chin-Lee <jchinlee@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Jao-ke Chin-Lee <jchinlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607313}

infra/config/global/luci-scheduler.cfg

@@ -244,6 +244,9 @@ trigger {
   triggers: "UBSan vptr Release"
   triggers: "UBSanVptr Linux"
   triggers: "VR Linux"
+  triggers: "WebKit Linux Trusty ASAN"
+  triggers: "WebKit Linux Trusty Leak"
+  triggers: "WebKit Linux Trusty MSAN"
   triggers: "Win 10 Fast Ring"
   triggers: "Win ASan Release Media"
   triggers: "Win ASan Release"