Make chrome.power sample extension work across updates.

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

 // Copyright (c) 2013 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.
 
 /**
  * States that the extension can be in.
  */
 var StateEnum = {
   DISABLED: 'disabled',
   DISPLAY: 'display',
@@ skipping 77 matching lines @@
         break;
       default:
         throw 'Invalid state "' + state + '"';
     }
   });
 });
 
 chrome.runtime.onStartup.addListener(function() {
   loadSavedState(function(state) { setState(state); });
 });
+
+chrome.runtime.onInstalled.addListener(function(details) {
+  loadSavedState(function(state) { setState(state); });

[Matt Perry, 2014/09/19 19:47:27]

I assume loadSavedState can be called multiple times without a problem. I
mention this because you might get an onInstalled event and onStartup event one
after the other, e.g. when Chrome itself updates.

[Daniel Erat, 2014/09/19 19:53:11]

yep, this should be fine. the locks don't stack and setState() blows away
whatever was there already, so the second duplicated call should just be a
no-op.

+});