Convert SysInfo::AmountOfFreeDiskSpace from wstring to FilePath.

net/disk_cache/backend_impl.cc

Index: net/disk_cache/backend_impl.cc
diff --git a/net/disk_cache/backend_impl.cc b/net/disk_cache/backend_impl.cc
index 0ce72143d3e3c2d96d173e870bef4789dec9cb9f..1dc439a72089b2fd1efab53818b122585d9c17de 100644
--- a/net/disk_cache/backend_impl.cc
+++ b/net/disk_cache/backend_impl.cc
@@ -1029,7 +1029,7 @@ void BackendImpl::AdjustMaxCacheSize(int table_len) {
   DCHECK(!table_len || data_->header.magic);
 
   // The user is not setting the size, let's figure it out.
-  int64 available = base::SysInfo::AmountOfFreeDiskSpace(path_.ToWStringHack());
+  int64 available = base::SysInfo::AmountOfFreeDiskSpace(path_);
   if (available < 0) {
     max_size_ = kDefaultCacheSize;
     return;