Moving away from shell api to support long path names on windows for filesystem.

base/file_path.h

Index: base/file_path.h
===================================================================
--- base/file_path.h	(revision 68690)
+++ base/file_path.h	(working copy)
@@ -151,6 +151,12 @@
   // The character used to identify a file extension.
   static const CharType kExtensionSeparator;
 
+#if defined(OS_WIN)
+  // Path length is limited to 260 on windows unless prefixed
+  // with a special extended path prefix.
+  static const CharType kExtendedPathPrefix[];
+#endif
+
   FilePath();
   FilePath(const FilePath& that);
   explicit FilePath(const StringType& path);
@@ -307,6 +313,11 @@
   FilePath NormalizeWindowsPathSeparators() const;
 #endif
 
+#if defined(OS_WIN)
+  // On windows, returns whether or not path starts with extended path prefix.
+  bool StartsWithExtendedPathPrefix() const;
+#endif
+
   // Compare two strings in the same way the file system does.
   // Note that these always ignore case, even on file systems that are case-
   // sensitive. If case-sensitive comparison is ever needed, add corresponding