Use input_api.ReadFile() instead of rolling out its own.

PRESUBMIT.py

 #!/usr/bin/python
 # Copyright (c) 2009 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
 details on the presubmit API built into gcl.
 """
 
 # Files with these extensions will be considered source files.
 SOURCE_FILE_EXTENSIONS = [
     '.c', '.cc', '.cpp', '.h', '.m', '.mm', '.py', '.mk', '.am', '.json',
 ]
 EXCLUDED_PATHS = [
     r"breakpad[\\\/].*",
     r"chrome[\\\/]Debug[\\\/].*",
     r"chrome[\\\/]Release[\\\/].*",
     r"sconsbuild[\\\/].*",
     r"xcodebuild[\\\/].*",
     r"skia[\\\/].*",
     r".*third_party[\\\/].*",
     r"v8[\\\/].*",
 ]
 
-def ReadFile(path):
-  """Given a path, returns the full contents of the file.
-
-  Reads files in binary format.
-  """
-  fo = open(path, 'rb')
-  try:
-    contents = fo.read()
-  finally:
-    fo.close()
-  return contents
-
 
 def CheckChangeOnUpload(input_api, output_api):
   # TODO(maruel): max_cols is temporarily disabled. Reenable once the source
   # tree is in better shape.
   results = []
   results.extend(LocalChecks(input_api, output_api, max_cols=0))
   results.extend(input_api.canned_checks.CheckChangeHasBugField(input_api,
                                                                 output_api))
   results.extend(input_api.canned_checks.CheckChangeHasTestField(input_api,
                                                                  output_api))
@@ skipping 44 matching lines @@
     found = False
     for item in excluded_paths:
       if item.match(path):
         found = True
         break
     if found:
       continue
 
     # Need to read the file ourselves since AffectedFile.NewContents()
     # will normalize line endings.
-    contents = ReadFile(f.AbsoluteLocalPath())
+    contents = input_api.ReadFile(f)
     if '\r' in contents:
       cr_files.append(path)
 
     # Check that the file ends in one and only one newline character.
     if len(contents) > 0 and (contents[-1:] != "\n" or contents[-2:-1] == "\n"):
       eof_files.append(path)
 
     local_errors = []
     # Remove end of line character.
     lines = contents.splitlines()
@@ skipping 70 matching lines @@
       # stable enough and it seems to work fine.
       outputs.append(output_api.PresubmitNotifyResult(
           'You should try the patch first.'))
     else:
       # Another HTTP error happened, warn the user.
       # TODO(maruel): Change to a PresubmitPromptWarning once it deemed to work
       # fine.
       outputs.append(output_api.PresubmitNotifyResult(
           'Got %s while looking for try job status.' % str(e)))
   return outputs