Mojo: Run mojo_shell_tests on trybots on all platforms.

testing/buildbot/chromium_trybot.json

 {
   "compile_targets": [
     "all"
   ],
   "gtest_tests": [
     "accessibility_unittests",
     "app_list_unittests",
     {
       "test": "base_unittests",
       "swarming": {
@@ skipping 82 matching lines @@
     "media_unittests",
     "message_center_unittests",
     "mojo_apps_js_unittests",
     "mojo_common_unittests",
     "mojo_js_unittests",
     "mojo_public_bindings_unittests",
     "mojo_public_environment_unittests",
     "mojo_public_system_unittests",
     "mojo_public_utility_unittests",
     "mojo_service_manager_unittests",
+    "mojo_shell_tests",
     "mojo_system_unittests",
     {
       "test": "nacl_loader_unittests",
       "platforms": ["linux"]
     },
     {
       "test": "net_unittests",
       "swarming": {
         "can_use_on_swarming_builders": true
       }
@@ skipping 45 matching lines @@
     },
     {
       "test": "ash_unittests",
       "platforms": ["win"]
     },
     {
       "test": "aura_unittests",
       "platforms": ["linux", "win"]
     },
     {
-      "test": "mojo_shell_tests",
-      "platforms": ["linux"]
-    },
-    {
       "test": "mojo_view_manager_unittests",
       "platforms": ["linux", "win"]
     },
     {
       "test": "views_unittests",
       "platforms": ["linux", "win"]
     },
     {
       "test": "sandbox_linux_unittests",
       "platforms": ["linux"],
@@ skipping 28 matching lines @@
     "tools/perf/.*",
     "tools/telemetry/.*",
     "tools/whitespace.txt"
   ],
 
   "filter_builders": [
     "linux_chromium_clang_dbg",
     "mac_chromium_rel"
   ]
 }