Update from https://crrev.com/312398

tools/vim/chromium.ycm_extra_conf.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.
 
 # Autocompletion config for YouCompleteMe in Chromium.
 #
 # USAGE:
 #
 #   1. Install YCM [https://github.com/Valloric/YouCompleteMe]
 #          (Googlers should check out [go/ycm])
@@ skipping 21 matching lines @@
 #     for everything I've used it for.
 #
 #   * That whole ninja & clang thing? We could support other configs if someone
 #     were willing to write the correct commands and a parser.
 #
 #   * This has only been tested on gPrecise.
 
 
 import os
 import os.path
+import re
 import subprocess
 import sys
 
 
+def SystemIncludeDirectoryFlags():
+  """Determines compile flags to include the system include directories.
+
+  Use as a workaround for https://github.com/Valloric/YouCompleteMe/issues/303
+
+  Returns:
+    (List of Strings) Compile flags to append.
+  """
+  try:
+    with open(os.devnull, 'rb') as DEVNULL:
+      output = subprocess.check_output(['clang', '-v', '-E', '-x', 'c++', '-'],
+                                       stdin=DEVNULL, stderr=subprocess.STDOUT)
+  except (FileNotFoundError, subprocess.CalledProcessError):
+    return []
+  includes_regex = r'#include <\.\.\.> search starts here:\s*' \
+                   r'(.*?)End of search list\.'
+  includes = re.search(includes_regex, output.decode(), re.DOTALL).group(1)
+  flags = []
+  for path in includes.splitlines():
+    path = path.strip()
+    if os.path.isdir(path):
+      flags.append('-isystem')
+      flags.append(path)
+  return flags
+
+
+_system_include_flags = SystemIncludeDirectoryFlags()
+
 # Flags from YCM's default config.
 flags = [
 '-DUSE_CLANG_COMPLETER',
 '-std=c++11',
 '-x',
 'c++',
 ]
 
 
 def PathExists(*args):
   return os.path.exists(os.path.join(*args))
 
 
 def FindChromeSrcFromFilename(filename):
   """Searches for the root of the Chromium checkout.
 
   Simply checks parent directories until it finds .gclient and src/.
 
   Args:
     filename: (String) Path to source file being edited.
 
   Returns:
     (String) Path of 'src/', or None if unable to find.
   """
   curdir = os.path.normpath(os.path.dirname(filename))
-  while not (PathExists(curdir, 'src') and PathExists(curdir, 'src', 'DEPS')
-             and (PathExists(curdir, '.gclient')
-                  or PathExists(curdir, 'src', '.git'))):
+  while not (os.path.basename(os.path.realpath(curdir)) == 'src'
+             and PathExists(curdir, 'DEPS')
+             and (PathExists(curdir, '..', '.gclient')
+                  or PathExists(curdir, '.git'))):
     nextdir = os.path.normpath(os.path.join(curdir, '..'))
     if nextdir == curdir:
       return None
     curdir = nextdir
-  return os.path.join(curdir, 'src')
+  return curdir
 
 
 def GetClangCommandFromNinjaForFilename(chrome_root, filename):
   """Returns the command line to build |filename|.
 
   Asks ninja how it would build the source file. If the specified file is a
   header, tries to find its companion source file first.
 
   Args:
     chrome_root: (String) Path to src/.
@@ skipping 99 matching lines @@
     filename: (String) Path to source file being edited.
 
   Returns:
     (Dictionary)
       'flags': (List of Strings) Command line flags.
       'do_cache': (Boolean) True if the result should be cached.
   """
   chrome_root = FindChromeSrcFromFilename(filename)
   chrome_flags = GetClangCommandFromNinjaForFilename(chrome_root,
                                                      filename)
-  final_flags = flags + chrome_flags
+  final_flags = flags + chrome_flags + _system_include_flags
 
   return {
     'flags': final_flags,
     'do_cache': True
   }