Mac: Add AssertIOAllowed() call to CopyFile()

base/file_util_mac.mm

Index: base/file_util_mac.mm
diff --git a/base/file_util_mac.mm b/base/file_util_mac.mm
index 811799c39fe0aa02ece3133851602a74a8a3be00..43bf6e9c744eeea77c7e81ab4edb521668ca28ed 100644
--- a/base/file_util_mac.mm
+++ b/base/file_util_mac.mm
@@ -10,6 +10,7 @@
 #include "base/basictypes.h"
 #include "base/file_path.h"
 #include "base/string_util.h"
+#include "base/thread_restrictions.h"
 
 namespace file_util {
 
@@ -26,6 +27,7 @@ bool GetShmemTempDir(FilePath* path) {
 }
 
 bool CopyFile(const FilePath& from_path, const FilePath& to_path) {
+  base::ThreadRestrictions::AssertIOAllowed();
   return (copyfile(from_path.value().c_str(),
                    to_path.value().c_str(), NULL, COPYFILE_ALL) == 0);
 }