Make build/include_what_you_use more consistent

cpplint.py

 #!/usr/bin/env python
 #
 # Copyright (c) 2009 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #    * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
@@ skipping 5627 matching lines @@
 
     for pattern, template, header in _re_pattern_algorithm_header:
       if pattern.search(line):
         required[header] = (linenum, template)
 
     # The following function is just a speed up, no semantics are changed.
     if not '<' in line:  # Reduces the cpu time usage by skipping lines.
       continue
 
     for pattern, template, header in _re_pattern_templates:
-      if pattern.search(line):
-        required[header] = (linenum, template)
+      matched = pattern.search(line)
+      if matched:
+        # Don't warn about IWYU in non-STL namespaces:
+        # (We check only the first match per line; good enough.)
+        prefix = line[:matched.start()]
+        if prefix.endswith('std::') or not prefix.endswith('::'):
+          required[header] = (linenum, template)
 
   # The policy is that if you #include something in foo.h you don't need to
   # include it again in foo.cc. Here, we will look at possible includes.
   # Let's flatten the include_state include_list and copy it into a dictionary.
   include_dict = dict([item for sublist in include_state.include_list
                        for item in sublist])
 
   # Did we find the header for this file (if any) and successfully load it?
   header_found = False
 
@@ skipping 654 matching lines @@
   _cpplint_state.ResetErrorCounts()
   for filename in filenames:
     ProcessFile(filename, _cpplint_state.verbose_level)
   _cpplint_state.PrintErrorCounts()
 
   sys.exit(_cpplint_state.error_count > 0)
 
 
 if __name__ == '__main__':
   main()