Auto merge of #11717 - izgzhen:filepicker, r=Manishearth

Add filepicker

Add file picker based on tinyfiledialog to the file manager implementation.

Changes:
- [x] Add the picker invocation code
- [x] Rewrite unit test to accommodate the change
- [x] Patch up `htmlinputelement` to make things work

<!-- Please describe your changes on the following line: -->

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes are related to #11131.

<!-- Either: -->
- [x] There are tests for these changes OR

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- 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/11717)
<!-- Reviewable:end -->

tests/unit/net/filemanager_thread.rs

@@ -3,15 +3,29 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use ipc_channel::ipc::{self, IpcSender};
-use net::filemanager_thread::FileManagerThreadFactory;
-use net_traits::filemanager_thread::{FileManagerThreadMsg, FileManagerThreadError};
+use net::filemanager_thread::{FileManagerThreadFactory, UIProvider};
+use net_traits::filemanager_thread::{FilterPattern, FileManagerThreadMsg, FileManagerThreadError};
 use std::fs::File;
 use std::io::Read;
 use std::path::PathBuf;
 
+const TEST_PROVIDER: &'static TestProvider = &TestProvider;
+
+struct TestProvider;
+
+impl UIProvider for TestProvider {
+    fn open_file_dialog(&self, _: &str, _: Option<(&[&str], &str)>) -> Option<String> {
+        Some("test.txt".to_string())
+    }
+
+    fn open_file_dialog_multi(&self, _: &str, _: Option<(&[&str], &str)>) -> Option<Vec<String>> {
+        Some(vec!["test.txt".to_string()])
+    }
+}
+
 #[test]
 fn test_filemanager() {
-    let chan: IpcSender<FileManagerThreadMsg> = FileManagerThreadFactory::new();
+    let chan: IpcSender<FileManagerThreadMsg> = FileManagerThreadFactory::new(TEST_PROVIDER);
 
     // Try to open a dummy file "tests/unit/net/test.txt" in tree
     let mut handler = File::open("test.txt").expect("test.txt is stolen");
@@ -20,11 +34,13 @@ fn test_filemanager() {
     handler.read_to_end(&mut test_file_content)
            .expect("Read tests/unit/net/test.txt error");
 
+    let patterns = vec![FilterPattern(".txt".to_string())];
+
 
     {
         // Try to select a dummy file "tests/unit/net/test.txt"
         let (tx, rx) = ipc::channel().unwrap();
-        chan.send(FileManagerThreadMsg::SelectFile(tx)).unwrap();
+        chan.send(FileManagerThreadMsg::SelectFile(patterns.clone(), tx)).unwrap();
         let selected = rx.recv().expect("File manager channel is broken")
                                 .expect("The file manager failed to find test.txt");
 
@@ -66,7 +82,7 @@ fn test_filemanager() {
 
     {
         let (tx, rx) = ipc::channel().unwrap();
-        let _ = chan.send(FileManagerThreadMsg::SelectFile(tx));
+        let _ = chan.send(FileManagerThreadMsg::SelectFile(patterns.clone(), tx));
 
         assert!(rx.try_recv().is_err(), "The thread should not respond normally after exited");
     }