Added WARN_UNUSED_RESULT to ScopedTempDir methods.

chrome/service/service_utility_process_host.cc

Index: chrome/service/service_utility_process_host.cc
diff --git a/chrome/service/service_utility_process_host.cc b/chrome/service/service_utility_process_host.cc
index 859e7259f2e404d2ed596e64a3d395da6837762b..d8befd1fc3877a80bb7d260088b59b49ad791fc4 100644
--- a/chrome/service/service_utility_process_host.cc
+++ b/chrome/service/service_utility_process_host.cc
@@ -194,7 +194,12 @@ void ServiceUtilityProcessHost::Client::MetafileAvailable(
   // The metafile was created in a temp folder which needs to get deleted after
   // we have processed it.
   ScopedTempDir scratch_metafile_dir;
-  scratch_metafile_dir.Set(metafile_path.DirName());
+  if (!scratch_metafile_dir.Set(metafile_path.DirName())) {
+    // This will happen if metafile_path is invalid. It could potentially
+    // be strengthened to a CHECK.
+    OnRenderPDFPagesToMetafileFailed();
+    return;
+  }
 #if defined(OS_WIN)
   printing::NativeMetafile metafile;
   if (!metafile.CreateFromFile(metafile_path)) {