[android log] Add documentation and presubmit checks for log usage.

PRESUBMIT.py

 # Copyright (c) 2012 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.
 
 """Top-level presubmit script for Chromium.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into depot_tools.
 """
 
@@ skipping 1282 matching lines @@
     import checkstyle
   finally:
     # Restore sys.path to what it was before.
     sys.path = original_sys_path
 
   return checkstyle.RunCheckstyle(
       input_api, output_api, 'tools/android/checkstyle/chromium-style-5.0.xml',
       black_list=_EXCLUDED_PATHS + input_api.DEFAULT_BLACK_LIST)
 
 
+def _CheckNoNewUtilLogUsage(input_api, output_api):
+  """Checks that new logs are using org.chromium.base.Log."""
+
+  chromium_log_import_pattern = input_api.re.compile(
+      r'^import org\.chromium\.base\.Log;$', input_api.re.MULTILINE);
+  log_pattern = input_api.re.compile(r'^\s*(android\.util\.)?Log\.\w')
+  sources = lambda x: input_api.FilterSourceFile(x, white_list=(r'.*\.java$',))
+
+  errors = []
+
+  for f in input_api.AffectedSourceFiles(sources):
+    if chromium_log_import_pattern.search(input_api.ReadFile(f)) is not None:
+      # Uses org.chromium.base.Log already
+      continue
+
+    for line_num, line in f.ChangedContents():
+      if log_pattern.search(line):
+        errors.append("%s:%d" % (f.LocalPath(), line_num))
+
+  results = []
+  if len(errors):
+    results.append(output_api.PresubmitPromptWarning(
+        'Please use org.chromium.base.Log for new logs.\n' +
+        'See base/android/java/src/org/chromium/base/README_logging.md ' +
+        'or contact dgn@chromium.org for more info.',
+        errors))
+  return results
+
+
 def _CheckForCopyrightedCode(input_api, output_api):
   """Verifies that newly added code doesn't contain copyrighted material
   and is properly licensed under the standard Chromium license.
 
   As there can be false positives, we maintain a whitelist file. This check
   also verifies that the whitelist file is up to date.
   """
   import sys
   original_sys_path = sys.path
   try:
@@ skipping 148 matching lines @@
   results.extend(_CheckForAnonymousVariables(input_api, output_api))
   results.extend(_CheckCygwinShell(input_api, output_api))
   results.extend(_CheckUserActionUpdate(input_api, output_api))
   results.extend(_CheckNoDeprecatedCSS(input_api, output_api))
   results.extend(_CheckNoDeprecatedJS(input_api, output_api))
   results.extend(_CheckParseErrors(input_api, output_api))
   results.extend(_CheckForIPCRules(input_api, output_api))
   results.extend(_CheckForCopyrightedCode(input_api, output_api))
   results.extend(_CheckForWindowsLineEndings(input_api, output_api))
   results.extend(_CheckSingletonInHeaders(input_api, output_api))
+  results.extend(_CheckNoNewUtilLogUsage(input_api, output_api))
 
   if any('PRESUBMIT.py' == f.LocalPath() for f in input_api.AffectedFiles()):
     results.extend(input_api.canned_checks.RunUnitTestsInDirectory(
         input_api, output_api,
         input_api.PresubmitLocalPath(),
         whitelist=[r'^PRESUBMIT_test\.py$']))
   return results
 
 
 def _CheckAuthorizedAuthor(input_api, output_api):
@@ skipping 292 matching lines @@
     # Explicitly iterate over copies of dicts since we mutate them.
     for master in builders.keys():
       for builder in builders[master].keys():
         # Do not trigger presubmit builders, since they're likely to fail
         # (e.g. OWNERS checks before finished code review), and we're
         # running local presubmit anyway.
         if 'presubmit' in builder:
           builders[master].pop(builder)
 
   return builders