Add mojo python bindings tests to the waterfalls.

scripts/slave/recipes/chromium.expected/full_client_skia_Linux_Builder.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "client.skia",
       "--builder",
       "Linux Builder",
@@ skipping 98 matching lines @@
       "--src-dir",
       "[SLAVE_BUILD]/src",
       "--build-tool",
       "ninja",
       "--compiler",
       "goma",
       "--goma-dir",
       "[BUILD]/goma",
       "--",
       "chrome",
-      "chromium_swarm_tests"
+      "chromium_swarm_tests",
+      "mojo_public_test_interfaces",
+      "mojo_python"
     ],
     "name": "compile"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]/src/buildtools/checkdeps/checkdeps.py",
       "--json",
       "/path/to/tmp/json"
@@ skipping 17 matching lines @@
       "--build_revision",
       "143121",
       "--factory-properties",
       "{\"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"buildername\": \"Linux Builder\", \"buildnumber\": 571, \"mastername\": \"client.skia\", \"parent_buildername\": null, \"recipe\": \"chromium\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}",
       "--build-properties",
       "{\"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"buildername\": \"Linux Builder\", \"buildnumber\": 571, \"mastername\": \"client.skia\", \"parent_buildername\": null, \"recipe\": \"chromium\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}"
     ],
     "name": "package build"
   }
 ]