Fix Chrome OS spelling in documentation

R=mkearney@chromium.org

Review URL: https://codereview.chromium.org/721033003

Cr-Commit-Position: refs/heads/master@{#310192}

chrome/common/extensions/docs/templates/articles/app_codelab_alarms.html

@@ -156,7 +156,7 @@ in the Console every time the alarm "rings":</p>
 
 <ul>
   <li>Even when you close the Todo app window, the alarms will keep coming.</li>
-  <li>On platforms other than ChromeOS, if you completely close all Chrome browser instances, alarms won't trigger.</li>
+  <li>On platforms other than Chrome OS, if you completely close all Chrome browser instances, alarms won't trigger.</li>
 </ul>
 
 <p>Let's go over some of the pieces in <em>alarms.js</em> that use <code>chrome.alarms</code> methods one by one.</p>

chrome/common/extensions/docs/templates/articles/manifest/file_handlers.html

@@ -52,6 +52,6 @@ compatibility, <code>title</code> should always be the name of the app.
 To handle files, apps also need to declare the $(ref:fileSystem)
 permission. Apps can then be passed files in the $(ref:app.runtime.onLaunched)
 event - either from the system
-file manager (currently supported on ChromeOS only) or by providing
+file manager (currently supported on Chrome OS only) or by providing
 a path on the <a href="../first_app#open">command line</a>.
 </p>

chrome/common/extensions/docs/templates/articles/manifest/offline_enabled.html

@@ -16,7 +16,7 @@ required and <code>"offline_enabled"</code> defaults to <code>false</code>.
 <p>
 The <code>"offline_enabled"</code> value is also used to determine whether a
 network connectivity check will be performed when launching an app in <a href="/apps/manifest/kiosk_enabled">
-ChromeOS kiosk mode</a>. A network connectivity check will be performed when
+Chrome OS kiosk mode</a>. A network connectivity check will be performed when
 apps are not offline enabled, and app launching put on hold until the device
 obtains connectivity to the Internet.
 </p>

chrome/common/extensions/docs/templates/articles/richNotifications.html

@@ -59,7 +59,7 @@ Notifications show up in a user's system tray,
 and stay in the system tray until the user dismisses them.
 On most platforms,
 the bell icon is lit when there's new notifications;
-On ChromeOS,
+On Chrome OS,
 the system tray keeps a count of all new notifications.
 Once a users sees the notifications in the system tray,
 the count is reset to zero;

chrome/common/extensions/docs/templates/intros/commands.html

@@ -85,7 +85,7 @@ code.
 the browser does not have focus, the shortcut will be inactive. On desktop
 Chrome, Commands can instead have global scope, as of version 35, and will then
 also work while Chrome does *not* have focus. NOTE: The exception here is
-ChromeOS, where global commands are not allowed at the moment.</p>
+Chrome OS, where global commands are not allowed at the moment.</p>
 
 <p>The user is free to designate any shortcut as global using the UI in
 chrome://extensions \ Keyboard Shortcuts, but the extension developer is limited