chromium.android: Test a swarmed blink_platform_unittests.

This runs blink_platform_unittests twice on Marshmallow 64 bit Tester.
Once via non-swarming, and again on swarming.

Plan is to let this run for a bit and if it fails identically, fully swarm
the bot.

BUG=

Review-Url: https://codereview.chromium.org/2336063004
Cr-Commit-Position: refs/heads/master@{#418434}

testing/buildbot/chromium.android.json

@@ -3052,6 +3052,37 @@
       {
         "test": "blink_platform_unittests"
       },
+      {
+        "override_isolate_target": "blink_platform_unittests",
+        "swarming": {
+          "can_use_on_swarming_builders": true,
+          "cipd_packages": [
+            {
+              "cipd_package": "infra/tools/luci/logdog/butler/${platform}",
+              "location": "bin",
+              "revision": "git_revision:3ff24775a900b675866fbcacf2a8f98a18b2a16a"
+            }
+          ],
+          "dimension_sets": [
+            {
+              "device_os": "MMB29Q",
+              "device_type": "bullhead"
+            }
+          ],
+          "hard_timeout": 960,
+          "output_links": [
+            {
+              "link": [
+                "https://luci-logdog.appspot.com/v/?s",
+                "=android%2Fswarming%2Flogcats%2F",
+                "${TASK_ID}%2F%2B%2Funified_logcats"
+              ],
+              "name": "shard #${SHARD_INDEX} logcats"
+            }
+          ]
+        },
+        "test": "blink_platform_unittests"
+      },
       {
         "override_compile_targets": [
           "breakpad_unittests_deps"