Add [SecureContext] to additional WebUSB interfaces

This change updates the WebUSB WebIDL files to match the recently merged
spec pull request #142 by hiding interfaces which aren't useful in
insecure contexts.

Change-Id: I98625b2634e452c775601525300672d9440ddbcc
Reviewed-on: https://chromium-review.googlesource.com/1137435
Commit-Queue: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576316}

webusb/insecure-context.any.js

@@ -0,0 +1,22 @@
+// META: global=sharedworker
+'use strict';
+
+test(() => {
+  assert_false(isSecureContext);
+  assert_false('usb' in navigator);
+}, '"usb" should not be present on navigator in an insecure context.');
+
+[
+    'USB', 'USBAlternateInterface', 'USBConfiguration', 'USBConnectionEvent',
+    'USBDevice', 'USBEndpoint', 'USBInterface', 'USBInTransferResult',
+    'USBOutTransferResult', 'USBIsochronousInTransferResult',
+    'USBIsochronousOutTransferResult', 'USBIsochronousInTransferPacket',
+    'USBIsochronousOutTransferPacket',
+].forEach((symbol) => {
+  test(() => {
+    assert_false(isSecureContext);
+    assert_false(symbol in this)
+  }, '"' + symbol + '" should not be visible in an insecure context.');
+});
+
+done();