Extract external file systems handling from isolated context.

chrome/browser/chromeos/extensions/file_browser_private_api.cc

Index: chrome/browser/chromeos/extensions/file_browser_private_api.cc
diff --git a/chrome/browser/chromeos/extensions/file_browser_private_api.cc b/chrome/browser/chromeos/extensions/file_browser_private_api.cc
index e75c81cbdd3e48a2116d5f1dbf29c7106f632356..a478ef9aebf6738866522743598e43ae90acd8e5 100644
--- a/chrome/browser/chromeos/extensions/file_browser_private_api.cc
+++ b/chrome/browser/chromeos/extensions/file_browser_private_api.cc
@@ -515,7 +515,7 @@ class RequestLocalFileSystemFunction::LocalFileSystemCallbackDispatcher {
 
     // Grant R/W file permissions to the renderer hosting component
     // extension for all paths exposed by our local file system provider.
-    std::vector<FilePath> root_dirs = provider->GetRootDirectories();
+    std::vector<FilePath> root_dirs = provider->GetRootDirectories(true);
     for (size_t i = 0; i < root_dirs.size(); ++i) {
       ChildProcessSecurityPolicy::GetInstance()->GrantPermissionsForFile(
           child_id_, root_dirs[i],