1 files changed, 47 insertions, 0 deletions
diff --git a/testing/web-platform/tests/resources/chromium/webusb-child-test.js b/testing/web-platform/tests/resources/chromium/webusb-child-test.js
new file mode 100644
index 0000000000..21412f66b0
--- /dev/null
+++ b/testing/web-platform/tests/resources/chromium/webusb-child-test.js
@@ -0,0 +1,47 @@
+'use strict';
+
+// This polyfill prepares a child context to be attached to a parent context.
+// The parent must call navigator.usb.test.attachToContext() to attach to the
+// child context.
+(() => {
+  if (this.constructor.name === 'DedicatedWorkerGlobalScope' ||
+      this !== window.top) {
+
+    // Run Chromium specific set up code.
+    if (typeof MojoInterfaceInterceptor !== 'undefined') {
+      let messageChannel = new MessageChannel();
+      messageChannel.port1.onmessage = async (messageEvent) => {
+        if (messageEvent.data.type === 'Attach') {
+          messageEvent.data.interfaces.forEach(interfaceName => {
+            let interfaceInterceptor =
+                new MojoInterfaceInterceptor(interfaceName);
+            interfaceInterceptor.oninterfacerequest =
+              e => messageChannel.port1.postMessage({
+                type: interfaceName,
+                handle: e.handle
+              }, [e.handle]);
+            interfaceInterceptor.start();
+          });
+
+          // Wait for a call to GetDevices() to ensure that the interface
+          // handles are forwarded to the parent context.
+          try {
+            await navigator.usb.getDevices();
+          } catch (e) {
+            // This can happen in case of, for example, testing usb disallowed
+            // iframe.
+            console.error(`getDevices() throws error: ${e.name}: ${e.message}`);
+          }
+
+          messageChannel.port1.postMessage({ type: 'Complete' });
+        }
+      };
+
+      let message = { type: 'ReadyForAttachment', port: messageChannel.port2 };
+      if (typeof Window !== 'undefined')
+        parent.postMessage(message, '*', [messageChannel.port2]);
+      else
+        postMessage(message, [messageChannel.port2]);
+    }
+  }
+})();