Add VR instrumentation tests to FYI bot

Adds the chrome_public_test_apk instrumentation tests to the Android VR FYI
builder and limits it to VR-related tests using the functionality added in
https://bugs.chromium.org/p/chromium/issues/detail?id=658342

BUG=

Review-Url: https://codereview.chromium.org/2537633002
Cr-Commit-Position: refs/heads/master@{#435039}

testing/buildbot/chromium.fyi.json

@@ -894,6 +894,15 @@
         },
         "test": "vr_shell_unittests"
       }
+    ],
+    "instrumentation_tests": [
+      {
+        "args": [
+          "--test-filter",
+          "VrShellTest#*"
+        ],
+        "test": "chrome_public_test_apk"
+      }
     ]
   },
   "Android x64 Tests": {