Implement systemInfo.storage.onChanged event

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

Index: chrome/renderer/resources/extensions/experimental.system_info_storage_custom_bindings.js
diff --git a/chrome/renderer/resources/extensions/experimental.system_info_storage_custom_bindings.js b/chrome/renderer/resources/extensions/experimental.system_info_storage_custom_bindings.js
new file mode 100644
index 0000000000000000000000000000000000000000..0db72cd171bbc7bd6e828f74bbf5ef1bb0f076f7
--- /dev/null
+++ b/chrome/renderer/resources/extensions/experimental.system_info_storage_custom_bindings.js
@@ -0,0 +1,101 @@
+// 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 systemInfo.storage API.
+
+var chromeHidden = requireNative('chrome_hidden').GetChromeHidden();
+var validate = require('schemaUtils').validate;
+
+// The JSON schemas for extra parameters of addListener. Currently the IDL
+// parser doesn't support extra parameter for event definitions, see
+// http://crbug.com/163822. This is just a workaround to make the schemas
+// validation works for extra parameter event even if no defintion is given
+// in IDL file.
+var extraArgJSONSchemas =
+'{                                                                   ' +
+'  "type":"object",                                                  ' +
+'  "id":"experimental.systemInfo.storage.EventOption",               ' +
+'  "properties": {                                                   ' +
+'    "id": {"type": "string", "optional": false, "name":"id"},       ' +
+'    "changeThreshold": {                                            ' +
+'      "type": "integer", "optional": true, "name":"changeThreshold" ' +
+'    }                                                               ' +
+'  }                                                                 ' +
+'}';
+
+var EVENT_DELIMITER = '#';
+
+// StorageChangeEvent object. This is used for systemInfo.storage.onChanged
+// event with extra parameter supporting. Each invocation of addListener
+// creates a new named sub-event for the storage being watched.
+//
+// Example:
+//   chrome.experimental.systemInfo.storage.onChanged.addListener(
+//       callback, {id: <storage_id>, changeThreshold: <number>});
+//   ^ callback will only be called for the changes happening on the specified
+//   storage and the change of free space is greater than the changeThreshold.
+//
+function StorageChangeEvent(eventName, argSchemas, extraArgSchemas,
+                            opt_eventOptions) {
+  // StorageChangeEvent inherits from chrome.Event object.
+  chrome.Event.call(this, eventName, argSchemas, opt_eventOptions);
+  if (!extraArgSchemas) {
+    this.extraArgSchemas_ = [];
+    this.extraArgSchemas_.push(JSON.parse(extraArgJSONSchemas));
+  }
+  else
+    this.extraArgSchemas_ = extraArgSchemas;
+  this.subEvents_ = {};
+}
+
+StorageChangeEvent.prototype = new chrome.Event();
+
+StorageChangeEvent.prototype.addListener = function(cb, eventOption) {
+  if (!this.eventOptions_.supportsListeners)
+    throw new Error('This event does not support listeners');
+  validate(Array.prototype.slice.call(arguments, 1), this.extraArgSchemas_);
+
+  // The format of sub-event name is "this.eventName_#<id>#changeThreshold".
+  var subEventName = this.eventName_ + EVENT_DELIMITER + eventOption.id;
+  // Default changeBytes is 4096 bytes.
+  if (!eventOption.changeThreshold || eventOption.changeThreshold <= 0)
+    eventOption.changeThreshold = 4096;
+  subEventName += EVENT_DELIMITER + eventOption.changeThreshold;
+
+  this.listeners_.push({callback: cb});
+
+  // If the event is already being listened.
+  if (this.subEvents_[subEventName]) {
+    var subEvent = this.subEvents_[subEventName].event;
+    subEvent.addListener(cb);
+    return;
+  }
+
+  // Create a new event.
+  var subEvent = new chrome.Event(subEventName, this.argSchemas_);
+  this.subEvents_[subEventName] = {event: subEvent, id: eventOption.id};
+  subEvent.addListener(cb);
+}
+
+StorageChangeEvent.prototype.removeListener = function(cb) {
+  if (!this.eventOptions_.supportsListeners)
+    throw new Error('This event does not support listeners');
+  var idx;
+  while ((idx = this.findListener_(cb)) >= 0) {
+    this.listeners_.splice(idx, 1);
+  }
+
+  for (var eventName in this.subEvents_) {
+    var subEvent = this.subEvents_[eventName].event;
+    if (subEvent.hasListener(cb)) {
+      subEvent.removeListener(cb);
+      if (!subEvent.hasListeners()) {
+        delete this.subEvents_[eventName];
+      }
+    }
+  }
+}
+
+chromeHidden.registerCustomEvent('experimental.systemInfo.storage',
+                                 StorageChangeEvent);