Fix atom::PATH_END so it's greater than PATH_START. (#18339)

Previously the enum list ended with entries copied values
from base::PATH_ entries, so the subsequent entry (PATH_END)
had a value in (base::PATH_START..base::PATH_END].

This only a correctness patch. atom::PATH_END doesn't appear
to be used anywhere and it was the only atom::PATH_ enum
bitten by this.

atom/browser/atom_paths.h

@@ -28,19 +28,23 @@ enum {
 
 #if defined(OS_LINUX)
   DIR_APP_DATA,  // Application Data directory under the user profile.
-#else
+#endif
+
+  PATH_END,  // End of new paths. Those that follow redirect to base::DIR_*
+
+#if !defined(OS_LINUX)
   DIR_APP_DATA = base::DIR_APP_DATA,
 #endif
 
 #if defined(OS_POSIX)
-  DIR_CACHE = base::DIR_CACHE,  // Directory where to put cache data.
+  DIR_CACHE = base::DIR_CACHE  // Directory where to put cache data.
 #else
-  DIR_CACHE = base::DIR_APP_DATA,
+  DIR_CACHE = base::DIR_APP_DATA
 #endif
-
-  PATH_END
 };
 
+static_assert(PATH_START < PATH_END, "invalid PATH boundaries");
+
 }  // namespace atom
 
 #endif  // ATOM_BROWSER_ATOM_PATHS_H_