Rename all tbm2 metrics to start with lowercase & add PRESUBMIT

tracing/bin/validate_all_metrics

 #!/usr/bin/env python
 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import argparse
 import json
 import os
+import string
 import sys
 
 sys.path.insert(1, os.path.join(os.path.dirname(__file__), '..'))
 from tracing.metrics import discover
 import tracing_project
 
 
 def Main():
   all_registered_metrics = set(discover.DiscoverMetrics(
       ['/tracing/metrics/all_metrics.html']))
   all_modules = list(
       '/' + rel_path for rel_path in
       tracing_project.TracingProject().FindAllMetricsModuleRelPaths())
   all_possible_metrics = set(discover.DiscoverMetrics(all_modules))
   unregistered_metrics = all_possible_metrics - all_registered_metrics
   if unregistered_metrics:
     print ('These metrics are unregistered: %s. Please import their modules in '
            'tracing/tracing/metrics/all_metrics.html' %
            ', '.join(unregistered_metrics))
     return 1
-  else:
-    return 0
+  uppercased_metrics = []
+  for m in all_possible_metrics:
+    if str.isupper(m[0]):
+      uppercased_metrics.append(m)
+  if uppercased_metrics:
+    print ('These metrics must be renamed to start with a lower-case: %s' %
+           uppercased_metrics)
+    return 1
+  return 0
 
 if __name__ == '__main__':
   sys.exit(Main())