[CQ] Add fuchsia trybots to CQ experiment

TBR=sergiyb@chromium.org
NOTRY=true

Bug: chromium:772816
Change-Id: I532e2c05360547686844f73c56d021abcbeb46bf
Reviewed-on: https://chromium-review.googlesource.com/725280Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48663}

infra/config/cq.cfg

@@ -24,6 +24,10 @@ verifiers {
     buckets {
       name: "master.tryserver.v8"
       builders { name: "v8_android_arm_compile_rel" }
+      builders {
+        name: "v8_fuchsia_rel_ng"
+        experiment_percentage: 20
+      }
       builders { name: "v8_node_linux64_rel" }
       builders { name: "v8_linux64_asan_rel_ng" }
       builders {