chromium_tests: pass paths to runit.py and runtest.py for src/testing/scripts

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

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[build::bisect_tester]/resources/put_temp.py"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "saving url to temp file",
     "stdin": "http://build.chromium.org/p/tryserver.chromium.perf/json/builders/linux_perf_tester/builds/571",
@@ skipping 146 matching lines @@
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]/src/testing/scripts/get_compile_targets.py",
       "--output",
       "/path/to/tmp/json",
       "--",
       "--build-config-fs",
       "Release",
       "--paths",
-      "{\"build\": \"[BUILD]\", \"checkout\": \"[SLAVE_BUILD]/src\"}",
+      "{\"build\": \"[BUILD]\", \"checkout\": \"[SLAVE_BUILD]/src\", \"runit.py\": \"RECIPE_PACKAGE_REPO[build]/scripts/tools/runit.py\", \"runtest.py\": \"RECIPE_PACKAGE_REPO[build]/scripts/slave/runtest.py\"}",
       "--properties",
       "{\"buildername\": \"linux_perf_tester\", \"buildnumber\": 571, \"mastername\": \"tryserver.chromium.perf\", \"slavename\": \"TestSlavename\", \"target_platform\": \"linux\"}"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "get compile targets for scripts",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{}@@@",
       "@@@STEP_LOG_END@json.output@@@"
     ]
   },
@@ skipping 121 matching lines @@
     "~followup_annotations": [
       "@@@STEP_LINK@gsutil.upload@https://storage.cloud.google.com/chrome-perf/bisect-results/f7a7b4135624439cbd27fdd5133d74ec.results@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]