chrome_paths: refactor and sanitize cache directory handling

base/path_service_unittest.cc

Index: base/path_service_unittest.cc
diff --git a/base/path_service_unittest.cc b/base/path_service_unittest.cc
index c65f7a56ba2cee4e306f01b0a8481f21d3993b3f..4c41aedbb15afab42c302065d42591e0f632370c 100644
--- a/base/path_service_unittest.cc
+++ b/base/path_service_unittest.cc
@@ -21,12 +21,6 @@ namespace {
 bool ReturnsValidPath(int dir_type) {
   FilePath path;
   bool result = PathService::Get(dir_type, &path);
-#if defined(OS_POSIX)
-  // If chromium has never been started on this account, the cache path will not
-  // exist.
-  if (dir_type == base::DIR_USER_CACHE)
-    return result && !path.value().empty();
-#endif
   return result && !path.value().empty() && file_util::PathExists(path);
 }