Move chrome.experimental.app.onLaunched event handler to chrome.app.runtime.onLaunched.

chrome/common/extensions/docs/static/first_app.html

 <meta name="doc-family" content="apps">
 <div id="pageData-name" class="pageData">Create Your First App</div>
 <div id="pageData-showTOC" class="pageData">true</div>
 
 <p>
 This tutorial walks you through creating your first packaged app.
 Packaged apps are structured similarly to extensions
 so current developers will recognize the manifest and packaging methods.
 When you're done,
 you'll just need to produce a zip file of your code and assets
@@ skipping 54 matching lines @@
 </p>
 
 <h2 id="two">Step 2: Create the background script</h2>
 
 <p>
 Next create a new file called <code>background.js</code>
 with the following content:
 </p>
 
 <pre>
-chrome.experimental.app.onLaunched.addListener(function() {
+chrome.app.runtime.onLaunched.addListener(function() {
   chrome.app.window.create('window.html', {
     'width': 400,
     'height': 500
   });
 });
 </pre>
 
 <p>
 In the above sample code,
 the <a href="app_lifecycle.html#lifecycle">onLaunched event</a>
@@ skipping 73 matching lines @@
 
 <h3>Open new tab and launch</h3>
 
 <p>
 Once you've loaded your app,
 open a New Tab page
 and click on your new app icon.
 </p>
 
 <p class="backtotop"><a href="#top">Back to top</a></p>
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