Re-land alexbost's experimental Offscreen Tabs API work.

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

+// 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.
+
+// Custom bindings for the experimental offscreenTabs API.
+
+(function() {
+
+native function GetChromeHidden();
+
+GetChromeHidden().registerCustomHook(
+    'experimental.offscreenTabs', function(api) {
+  var apiFunctions = api.apiFunctions;
+
+  function maybeCopy(src, prop, dest) {
+    if (src[prop] != undefined) {
+      dest[prop] = src[prop];
+    }
+  };
+
+  function keyboardEventFilter(e) {
+    var result = {
+      "type": e.type,
+      "char": e.char,
+      "key": e.key,
+      "location": e.location,
+      "ctrlKey": e.ctrlKey,
+      "shiftKey": e.shiftKey,
+      "altKey": e.altKey,
+      "metaKey": e.metaKey,
+      "repeat": e.repeat,
+      "locale": e.locale
+    };
+    maybeCopy(e, "keyCode", result);
+    maybeCopy(e, "charCode", result);
+    return result;
+  };
+
+  function mouseEventFilter(e) {
+    var result = {
+      "type": e.type,
+      "screenX": e.screenX,
+      "screenY": e.screenY,
+      "clientX": e.clientX,
+      "clientY": e.clientY,
+      "ctrlKey": e.ctrlKey,
+      "shiftKey": e.shiftKey,
+      "altKey": e.altKey,
+      "metaKey": e.metaKey,
+      "button": e.button,
+      "buttons": e.buttons
+    };
+    maybeCopy(e, "deltaX", result);
+    maybeCopy(e, "deltaY", result);
+    maybeCopy(e, "deltaZ", result);
+    maybeCopy(e, "wheelDeltaX", result);
+    maybeCopy(e, "wheelDeltaY", result);
+    return result;
+  };
+
+  function validateFunc(args, filter) {
+    var newArgs = [];
+
+    for (var ii = 0; ii < args.length; ++ii) {
+      var arg = args[ii];
+      if (ii == 1 && typeof(arg) == 'object') {
+        arg = filter(arg);
+      }
+      newArgs.push(arg);
+    }
+
+    return newArgs;
+  };
+
+  function validateKeyboardEvent() {
+    return validateFunc(arguments, keyboardEventFilter);
+  }
+
+  function validateMouseEvent() {
+    return validateFunc(arguments, mouseEventFilter);
+  }
+
+  apiFunctions.setUpdateArgumentsPreValidate(
+      "experimental.offscreenTabs.sendKeyboardEvent", validateKeyboardEvent);
+  apiFunctions.setUpdateArgumentsPreValidate(
+      "experimental.offscreenTabs.sendMouseEvent", validateMouseEvent);
+});
+
+})();