Swarm media_unittests.

testing/buildbot/chromium_trybot.json

 {
   "compile_targets": [
     "all"
   ],
   "gtest_tests": [
     {
       "test": "accessibility_unittests",
       "swarming": {
         "can_use_on_swarming_builders": true
       }
@@ skipping 117 matching lines @@
       "test": "ipc_mojo_unittests",
       "platforms": ["linux"]
     },
     "ipc_tests",
     "jingle_unittests",
     {
       "test": "keyboard_unittests",
       "platforms": ["linux", "win"]
     },
     "media_perftests",
-    "media_unittests",
+    {
+      "test": "media_unittests",
+      "swarming": {
+        "can_use_on_swarming_builders": true
+      }
+    },
     {
       "test": "message_center_unittests",
       "swarming": {
         "can_use_on_swarming_builders": true
       }
     },
     "mojo_common_unittests",
     "mojo_public_bindings_unittests",
     "mojo_public_environment_unittests",
     "mojo_public_system_unittests",
@@ skipping 118 matching lines @@
   "non_filter_tests_builders": [
   ],
 
   "filter_compile_builders": [
     "win_chromium_compile_dbg",
     "win_chromium_rel_swarming",
     "win_chromium_x64_rel_swarming",
     "win8_chromium_rel"
   ]
 }