Add chrome.power extension API.

chrome/common/extensions/docs/examples/api/power/background.js

+/**
+ * Available levels of power-saving-overriding.
+ */
+var LevelEnum = {
+  DISABLED: '',
+  DISPLAY: 'display',
+  SYSTEM: 'system'
+};
+
+/**
+ * Key used for storing the current level in {localStorage}.
+ */
+var LEVEL_KEY = 'level';
+
+/**
+ * Current {LevelEnum}.
+ */
+var currentLevel = LevelEnum.DISABLED;
+
+/**
+ * Should the old {chrome.experimental.power} API be used rather than
+ * {chrome.power}?
+ */
+var useOldApi = !chrome.power;
+
+/**
+ * Returns the previously-used level.
+ * @return {string} Saved {LevelEnum} from local storage.
+ */
+function getInitialLevel() {
+  if (LEVEL_KEY in localStorage) {
+    var savedLevel = localStorage[LEVEL_KEY];
+    for (var key in LevelEnum) {
+      if (savedLevel == LevelEnum[key]) {
+        return savedLevel;
+      }
+    }
+  }
+  return LevelEnum.DISABLED;
+}
+
+/**
+ * Switches to a new power-saving-overriding level.
+ * @param {string} newLevel New {LevelEnum} to use.
+ */
+function setLevel(newLevel) {
+  var imagePrefix = 'night';
+  var title = '';
+
+  // The old API doesn't support the "system" level.
+  if (useOldApi && newLevel == LevelEnum.SYSTEM)
+    newLevel = LevelEnum.DISPLAY;
+
+  switch (newLevel) {
+    case LevelEnum.DISABLED:
+      (useOldApi ? chrome.experimental.power : chrome.power).releaseKeepAwake();
+      imagePrefix = 'night';
+      title = chrome.i18n.getMessage('disabledTitle');
+      break;
+    case LevelEnum.DISPLAY:
+      if (useOldApi)
+        chrome.experimental.power.requestKeepAwake(function() {});
+      else
+        chrome.power.requestKeepAwake('display');
+      imagePrefix = 'day';
+      title = chrome.i18n.getMessage('displayTitle');
+      break;
+    case LevelEnum.SYSTEM:
+      chrome.power.requestKeepAwake('system');
+      imagePrefix = 'sunset';
+      title = chrome.i18n.getMessage('systemTitle');
+      break;
+    default:
+      throw 'Invalid level "' + newLevel + '"';
+  }
+
+  currentLevel = newLevel;
+  localStorage[LEVEL_KEY] = currentLevel;
+
+  chrome.browserAction.setIcon({
+    path: {
+      '19': 'images/' + imagePrefix + '-19.png',
+      '38': 'images/' + imagePrefix + '-38.png'
+    }
+  });
+  chrome.browserAction.setTitle({title: title});
+}
+
+/**
+ * Cycles levels in response to browser action icon clicks.
+ */
+function handleClicked() {
+  switch (currentLevel) {
+    case LevelEnum.DISABLED:
+      setLevel(LevelEnum.DISPLAY);
+      break;
+    case LevelEnum.DISPLAY:
+      setLevel(useOldApi ? LevelEnum.DISABLED : LevelEnum.SYSTEM);
+      break;
+    case LevelEnum.SYSTEM:
+      setLevel(LevelEnum.DISABLED);
+      break;
+    default:
+      throw 'Invalid level "' + currentLevel + '"';
+  }
+}
+
+setLevel(getInitialLevel());
+chrome.browserAction.onClicked.addListener(handleClicked);