Update the child process security policy to use explicit permission grants.

chrome/browser/chromeos/extensions/file_manager/file_browser_handler_api.cc

Index: chrome/browser/chromeos/extensions/file_manager/file_browser_handler_api.cc
diff --git a/chrome/browser/chromeos/extensions/file_manager/file_browser_handler_api.cc b/chrome/browser/chromeos/extensions/file_manager/file_browser_handler_api.cc
index cfe538bee9ec841b580c205ecb36cc4f6d82b1a2..fb729d608e0cf99fde0e14fc3d0dc46d26697d80 100644
--- a/chrome/browser/chromeos/extensions/file_manager/file_browser_handler_api.cc
+++ b/chrome/browser/chromeos/extensions/file_manager/file_browser_handler_api.cc
@@ -381,10 +381,8 @@ void FileBrowserHandlerInternalSelectFileFunction::GrantPermissions() {
   external_provider->GrantFileAccessToExtension(extension_id(), virtual_path_);
 
   // Grant access to the selected file to target extensions render view process.
-  content::ChildProcessSecurityPolicy::GetInstance()->GrantPermissionsForFile(
-      render_view_host()->GetProcess()->GetID(),
-      full_path_,
-      file_handler_util::GetReadWritePermissions());
+  content::ChildProcessSecurityPolicy::GetInstance()->GrantCreateReadWriteFile(
+      render_view_host()->GetProcess()->GetID(), full_path_);
 }
 
 void FileBrowserHandlerInternalSelectFileFunction::Respond(bool success) {