Add PRESUBMIT to make sure that perf JSON configs are always up-to-date

tools/perf/PRESUBMIT.py

Index: tools/perf/PRESUBMIT.py
diff --git a/tools/perf/PRESUBMIT.py b/tools/perf/PRESUBMIT.py
index 25fe5f49f644c2145c85a5e8c0c4902170a7f783..13815ee7320cf7032b22b1677d4b30c66476a85f 100644
--- a/tools/perf/PRESUBMIT.py
+++ b/tools/perf/PRESUBMIT.py
@@ -18,6 +18,7 @@ def _CommonChecks(input_api, output_api):
 
   results.extend(_CheckWprShaFiles(input_api, output_api))
   results.extend(_CheckJson(input_api, output_api))
+  results.extend(_CheckPerfJsonUpToDate(input_api, output_api))
   results.extend(input_api.RunTests(input_api.canned_checks.GetPylint(
       input_api, output_api, extra_paths_list=_GetPathsToPrepend(input_api),
       pylintrc='pylintrc')))
@@ -38,6 +39,26 @@ def _GetPathsToPrepend(input_api):
   ]
 
 
+def _RunArgs(args, input_api):
+  p = input_api.subprocess.Popen(args, stdout=input_api.subprocess.PIPE,
+                                 stderr=input_api.subprocess.STDOUT)
+  out, _ = p.communicate()
+  return (out, p.returncode)
+
+
+def _CheckPerfJsonUpToDate(input_api, output_api):
+  results = []
+  perf_dir = input_api.PresubmitLocalPath()
+  out, return_code = _RunArgs([
+      input_api.python_executable,
+      input_api.os_path.join(perf_dir, 'generate_perf_json.py'),
+      '--validate-only'], input_api)
+  if return_code:
+      results.append(output_api.PresubmitError(
+          'Validating Perf JSON configs failed.', long_text=out))
+  return results
+
+
 def _CheckWprShaFiles(input_api, output_api):
   """Check whether the wpr sha files have matching URLs."""
   old_sys_path = sys.path