Experimental USB API implementation.

chrome/renderer/resources/extensions/experimental.usb_custom_bindings.js

Index: chrome/renderer/resources/extensions/experimental.usb_custom_bindings.js
diff --git a/chrome/renderer/resources/extensions/experimental.usb_custom_bindings.js b/chrome/renderer/resources/extensions/experimental.usb_custom_bindings.js
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+++ b/chrome/renderer/resources/extensions/experimental.usb_custom_bindings.js
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+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// TODO(gdk): This all looks very similar to the socket custom bindings, and for
+// a good reason, because they essentially do the same work. Refactor onEvent
+// bindings out of a per-extension mechanism into a generalized mechanism.
+
+  var experimentalUsbNatives = requireNative('experimental_usb');
+  var GetNextUsbEventId = experimentalUsbNatives.GetNextUsbEventId;
+
+  var chromeHidden = requireNative('chrome_hidden').GetChromeHidden();
+  var sendRequest = require('sendRequest').sendRequest;
+  var lazyBG = requireNative('lazy_background_page');
+
+  chromeHidden.registerCustomHook('experimental.usb', function(api) {
+      var apiFunctions = api.apiFunctions;
+
+      apiFunctions.setHandleRequest('findDevice', function() {
+          var args = arguments;
+          if (args[2] && args[2].onEvent) {
+            var id = GetNextUsbEventId();
+            args[2].srcId = id;
+            chromeHidden.usb.handlers[id] = args[2].onEvent;
+            lazyBG.IncrementKeepaliveCount();
+          }
+          sendRequest(this.name, args, this.definition.parameters);
+          return id;
+        });
+
+      chromeHidden.usb = {};
+      chromeHidden.usb.handlers = {};
+      chrome.experimental.usb.onEvent.addListener(function(event) {
+          var eventHandler = chromeHidden.usb.handlers[event.srcId];
+          if (eventHandler) {
+            switch (event.type) {
+              case 'transferComplete':
+                eventHandler({resultCode: event.resultCode, data: event.data});
+                break;
+              default:
+                console.error('Unexpected UsbEvent, type ' + event.type);
+                break;
+            }
+          }
+        });
+    });