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

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="35" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/11029)
<!-- Reviewable:end -->

components/net_traits/Cargo.toml

@@ -22,3 +22,4 @@ serde = "0.7"
 serde_macros = "0.7"
 url = {version = "1.0.0", features = ["heap_size"]}
 websocket = "0.17"
+uuid = { version = "0.2.2", features = ["v4", "serde"] }

components/net_traits/filemanager_thread.rs

@@ -0,0 +1,34 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use ipc_channel::ipc::IpcSender;
+use std::path::PathBuf;
+use uuid::Uuid;
+
+#[derive(Deserialize, Serialize)]
+pub enum FileManagerThreadMsg {
+    /// Select a single file, return triple (FileID, FileName, lastModified)
+    SelectFile(IpcSender<FileManagerResult<(Uuid, PathBuf, u64)>>),
+
+    /// Select multiple files, return a vector of triples
+    SelectFiles(IpcSender<FileManagerResult<Vec<(Uuid, PathBuf, u64)>>>),
+
+    /// Read file, return the bytes
+    ReadFile(IpcSender<FileManagerResult<Vec<u8>>>, Uuid),
+
+    /// Delete the FileID entry
+    DeleteFileID(Uuid),
+}
+
+pub type FileManagerResult<T> = Result<T, FileManagerThreadError>;
+
+#[derive(Deserialize, Serialize)]
+pub enum FileManagerThreadError {
+    /// The selection action is invalid, nothing is selected
+    InvalidSelection,
+    /// Failure to process file information such as file name, modified time etc.
+    FileInfoProcessingError,
+    /// Failure to read the file content
+    ReadFileError,
+}

components/net_traits/lib.rs

@@ -26,6 +26,7 @@ extern crate msg;
 extern crate serde;
 extern crate url;
 extern crate util;
+extern crate uuid;
 extern crate websocket;
 
 use hyper::header::{ContentType, Headers};
@@ -42,6 +43,7 @@ use websocket::header;
 
 pub mod bluetooth_scanfilter;
 pub mod bluetooth_thread;
+pub mod filemanager_thread;
 pub mod hosts;
 pub mod image_cache_thread;
 pub mod net_error_list;