Add presubmit check for copyright notice

PRESUBMIT.py

Index: PRESUBMIT.py
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index ae5a2183162c81026e8e382e6792b75fe362cc8c..d2e8ee6951cc5cf2c443d3e8efe1d7d03ac069c6 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -118,6 +118,38 @@ def _IfDefChecks(input_api, output_api):
   return results
 
 
+def _CopyrightChecks(input_api, output_api, source_file_filter=None):
+  results = []
+  year_pattern = r'\d{4}'
+  year_range_pattern = r'%s(-%s)?' % (year_pattern, year_pattern)
+  years_pattern = r'%s(,%s)*,?' % (year_range_pattern, year_range_pattern)
+  copyright_pattern = (
+      r'Copyright (\([cC]\) )?%s %s' % (years_pattern, '%s'))
+  owners = [
+    'ARM Ltd.',
+    'Code Aurora Forum. All rights reserved.',
+    'Google,? Inc\.?( All rights reserved.)?',
+    'Intel Inc.',
+    'Lua.org, PUC-Rio',
+    'Skia',
+    'The Android Open Source Project',
+    'The Chromium Authors. All rights reserved.',
+    'The Native Client Authors. All rights reserved.',

[borenet, 2015/03/23 14:38:05]

I just pulled these from existing copyright notices.  Are these all valid? 
Should I just check that there's a copyright notice at all, rather than having
an owner whitelist?  For that matter, there are a few files which have no
copyright owner, ie. "Copyright 2014".  Is that valid?

[mtklein, 2015/03/23 14:49:50]

Let's both exclude third_party ('Lua.org, PUC-Rio') and allow any non-empty
copyright holder ([^\w]+) ?

[borenet, 2015/03/23 17:20:35]

Done.

+  ]
+
+  for affected_file in input_api.AffectedSourceFiles(source_file_filter):
+    contents = input_api.ReadFile(affected_file, 'rb')
+    found = False
+    for owner in owners:
+      if re.search(copyright_pattern % owner, contents):
+        found = True
+        break
+    if not found:
+      results.append(output_api.PresubmitError(
+          '%s is missing a correct copyright header.' % affected_file))
+  return results
+
+
 def _CommonChecks(input_api, output_api):
   """Presubmit checks common to upload and commit."""
   results = []
@@ -132,6 +164,8 @@ def _CommonChecks(input_api, output_api):
           input_api, output_api, source_file_filter=sources))
   results.extend(_PythonChecks(input_api, output_api))
   results.extend(_IfDefChecks(input_api, output_api))
+  results.extend(_CopyrightChecks(input_api, output_api,
+                                  source_file_filter=sources))
   return results