Auto merge of #11029 - izgzhen:filemanager_thread, r=Manishearth

Add FileManagerThread

This is intended to support the File API implementation. Basically an event loop with three kinds of messages:

+ Select a file
+ Read a file with ID
+ Delete the ID from manager-owned map

The design decision in this PR is not the final (or best I think) version, welcome reviews :)

TODOs:

- [x] Add multiple file selection

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components/net/lib.rs

@@ -4,6 +4,7 @@
 
 #![feature(box_syntax)]
 #![feature(fnbox)]
+#![feature(fs_time)]
 #![feature(mpsc_select)]
 #![feature(plugin)]
 #![feature(plugin)]
@@ -50,6 +51,7 @@ pub mod cookie;
 pub mod cookie_storage;
 pub mod data_loader;
 pub mod file_loader;
+pub mod filemanager_thread;
 pub mod hsts;
 pub mod http_loader;
 pub mod image_cache_thread;