Update from https://crrev.com/333737

base/files/file_path.h

 // 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.
 
 // FilePath is a container for pathnames stored in a platform's native string
 // type, providing containers for manipulation in according with the
 // platform's conventions for pathnames.  It supports the following path
 // types:
 //
 //                   POSIX            Windows
@@ skipping 85 matching lines @@
 //    FilePath treats c://, c:\\, //, and \\ all equivalently.
 //    Reference:
 //    The Old New Thing, "Why is a drive letter permitted in front of UNC
 //    paths (sometimes)?", available at:
 //    http://blogs.msdn.com/oldnewthing/archive/2005/11/22/495740.aspx
 
 #ifndef BASE_FILES_FILE_PATH_H_
 #define BASE_FILES_FILE_PATH_H_
 
 #include <stddef.h>
+
+#include <iosfwd>
 #include <string>
 #include <vector>
 
 #include "base/base_export.h"
 #include "base/compiler_specific.h"
 #include "base/containers/hash_tables.h"
 #include "base/strings/string16.h"
 #include "base/strings/string_piece.h"  // For implicit conversions.
 #include "build/build_config.h"
 
 // Windows-style drive letter support and pathname separator characters can be
 // enabled and disabled independently, to aid testing.  These #defines are
 // here so that the same setting can be used in both the implementation and
 // in the unit test.
 #if defined(OS_WIN)
 #define FILE_PATH_USES_DRIVE_LETTERS
 #define FILE_PATH_USES_WIN_SEPARATORS
 #endif  // OS_WIN
 
+namespace base {
+
 class Pickle;
 class PickleIterator;
 
-namespace base {
-
 // An abstraction to isolate users from the differences between native
 // pathnames on different platforms.
 class BASE_EXPORT FilePath {
  public:
 #if defined(OS_POSIX)
   // On most platforms, native pathnames are char arrays, and the encoding
   // may or may not be specified.  On Mac OS X, native pathnames are encoded
   // in UTF-8.
   typedef std::string StringType;
 #elif defined(OS_WIN)
@@ skipping 286 matching lines @@
   // Remove trailing separators from this object.  If the path is absolute, it
   // will never be stripped any more than to refer to the absolute root
   // directory, so "////" will become "/", not "".  A leading pair of
   // separators is never stripped, to support alternate roots.  This is used to
   // support UNC paths on Windows.
   void StripTrailingSeparatorsInternal();
 
   StringType path_;
 };
 
+// This is required by googletest to print a readable output on test failures.
+// This is declared here for use in gtest-based unit tests but is defined in
+// the test_support_base target. Depend on that to use this in your unit test.
+// This should not be used in production code - call ToString() instead.
+void PrintTo(const FilePath& path, std::ostream* out);
+
 }  // namespace base
 
-// This is required by googletest to print a readable output on test failures.
-BASE_EXPORT extern void PrintTo(const base::FilePath& path, std::ostream* out);
-
 // Macros for string literal initialization of FilePath::CharType[], and for
 // using a FilePath::CharType[] in a printf-style format string.
 #if defined(OS_POSIX)
 #define FILE_PATH_LITERAL(x) x
 #define PRFilePath "s"
 #elif defined(OS_WIN)
 #define FILE_PATH_LITERAL(x) L ## x
 #define PRFilePath "ls"
 #endif  // OS_WIN
 
 // Provide a hash function so that hash_sets and maps can contain FilePath
 // objects.
 namespace BASE_HASH_NAMESPACE {
 
 template<>
 struct hash<base::FilePath> {
   size_t operator()(const base::FilePath& f) const {
     return hash<base::FilePath::StringType>()(f.value());
   }
 };
 
 }  // namespace BASE_HASH_NAMESPACE
 
 #endif  // BASE_FILES_FILE_PATH_H_