[FS] Simplify child URL calculation in DirectoryHandleImpl.

FileSystemURL doesn't round-trip well through GURL, and it's much
simpler to generate a child URL directly from the parent FileSystemURL
anyway, so simplify NativeFileSystemDirectoryHandleImpl::GetChildURL to
skip the conversions to/from GURL.

Bug: 1093653
Change-Id: I13d515ca3e25ed7c8deca1ceb913b7dea58ed67b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2362768
Auto-Submit: Marijn Kruisselbrink <mek@chromium.org>
Commit-Queue: Victor Costan <pwnall@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#800364}

content/browser/native_file_system/native_file_system_directory_handle_impl.cc

@@ -433,16 +433,10 @@ NativeFileSystemDirectoryHandleImpl::GetChildURL(
         "Name contains invalid characters.");
   }
 
-  std::string escaped_name =
-      net::EscapeQueryParamValue(basename, /*use_plus=*/false);
-
-  GURL parent_url = url().ToGURL();
-  std::string path = base::StrCat({parent_url.path(), "/", escaped_name});
-  GURL::Replacements replacements;
-  replacements.SetPathStr(path);
-  GURL child_url = parent_url.ReplaceComponents(replacements);
-
-  *result = file_system_context()->CrackURL(child_url);
+  const storage::FileSystemURL parent = url();
+  *result = file_system_context()->CreateCrackedFileSystemURL(
+      parent.origin(), parent.mount_type(),
+      parent.virtual_path().Append(base::FilePath::FromUTF8Unsafe(basename)));
   return native_file_system_error::Ok();
 }