Bug 1726476 - Adjust GetSandboxedRLBoxPath for the changes in rlbox_wasm2c_sandbox. r=nika

rlbox_wasm2c_sandbox was adjusted to avoid using LoadLibraryA (rejected by
build/clang-plugin/LoadLibraryUsageChecker.cpp), so we adjust
GetSandboxedRLBoxPath (which is used to feed it) to return an UTF-16
string on Windows.

Differential Revision: https://phabricator.services.mozilla.com/D123025

ipc/glue/LibrarySandboxPreload.cpp

@@ -12,7 +12,7 @@
 namespace mozilla {
 namespace ipc {
 
-nsCString GetSandboxedRLBoxPath() {
+PathString GetSandboxedRLBoxPath() {
   nsCOMPtr<nsIFile> libFile;
   nsresult rv = mozilla::BinaryPath::GetFile(getter_AddRefs(libFile));
   if (NS_FAILED(rv)) {
@@ -24,12 +24,7 @@ nsCString GetSandboxedRLBoxPath() {
     MOZ_CRASH("Library preload failure: Failed to get library file\n");
   }
 
-  PathString fullPath = libFile->NativePath();
-#ifdef XP_WIN
-  return NS_ConvertUTF16toUTF8(fullPath);
-#else
-  return fullPath;
-#endif
+  return libFile->NativePath();
 }
 
 PRLibrary* PreloadLibrary(const nsCString& path) {

ipc/glue/LibrarySandboxPreload.h

@@ -8,11 +8,11 @@
 #ifndef ipc_glue_LibrarySandboxPreload_h
 #define ipc_glue_LibrarySandboxPreload_h
 
-#include "nsString.h"
+#include "mozilla/FileUtils.h"
 
 namespace mozilla {
 namespace ipc {
-nsCString GetSandboxedRLBoxPath();
+PathString GetSandboxedRLBoxPath();
 void PreloadSandboxedDynamicLibrary();
 }  // namespace ipc
 }  // namespace mozilla