Add mojo python bindings tests to the waterfalls.

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

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "chromium.linux",
       "--builder",
       "Linux Tests",
@@ skipping 120 matching lines @@
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]/src/mojo/tools/run_mojo_python_tests.py",
       "--write-full-results-to",
       "/path/to/tmp/json"
     ],
     "name": "mojo_python_tests"
   },
   {
+    "cmd": [
+      "python",
+      "-u",
+      "[SLAVE_BUILD]/src/mojo/tools/run_mojo_python_bindings_tests.py",
+      "--write-full-results-to",
+      "/path/to/tmp/json",
+      "--build-dir",
+      "[SLAVE_BUILD]/src/out"
+    ],
+    "name": "mojo_python_bindings_tests"
+  },
+  {
     "allow_subannotations": true,
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/runtest.py",
       "--target",
       "Release",
       "--xvfb",
       "--factory-properties",
       "{\"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"buildername\": \"Linux Tests\", \"buildnumber\": 571, \"mastername\": \"chromium.linux\", \"parent_build_archive_url\": \"gs://test-domain/test-archive.zip\", \"parent_buildername\": \"Linux Builder\", \"parent_got_revision\": \"1111111\", \"recipe\": \"chromium\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}",
@@ skipping 54 matching lines @@
       "--metadata",
       "blink_revision=124383",
       "--metadata",
       "build_number=571",
       "--write-full-results-to",
       "/path/to/tmp/json"
     ],
     "name": "telemetry_perf_unittests"
   }
 ]