Add ScopedAllowIO to allow get of FILE_EXE etc paths from non-IO-thread.

base/base_paths_mac.mm

Index: base/base_paths_mac.mm
diff --git a/base/base_paths_mac.mm b/base/base_paths_mac.mm
index 839df0d7cc981d36f1759bea8ea5ba360745c091..9576237110c83599f0f4f4b30cf6b5ff07ff0c09 100644
--- a/base/base_paths_mac.mm
+++ b/base/base_paths_mac.mm
@@ -18,6 +18,7 @@
 #include "base/mac/foundation_util.h"
 #include "base/path_service.h"
 #include "base/strings/string_util.h"
+#include "base/threading/thread_restrictions.h"
 #include "build/build_config.h"
 
 namespace {
@@ -39,6 +40,8 @@ void GetNSExecutablePath(base::FilePath* path) {
   // FilePath::DirName() work incorrectly, convert it to absolute path so that
   // paths such as DIR_SOURCE_ROOT can work, since we expect absolute paths to
   // be returned here.
+  // TODO(bauerb): http://crbug.com/259796, http://crbug.com/373477
+  base::ThreadRestrictions::ScopedAllowIO allow_io;
   *path = base::MakeAbsoluteFilePath(base::FilePath(executable_path));
 }