Enable the Commands API.

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

 <h2 id="manifest">Manifest</h2>
 <p>
 You must set manifest_version to (at least) 2 to use this API.
 </p>
 
 <h2 id="usage">Usage</h2>
 <p>The commands API allows you to define specific commands, and bind them to a
 default key combination. Each command your extension accepts must be listed in
 the manifest as an attribute of the 'commands' manifest key. An extension can
 have many commands but only 4 suggested keys can be specified. The user can
@@ skipping 56 matching lines @@
   console.log('Command:', command);
 });
 </pre>
 
 <p>The '_execute_browser_action' and '_execute_page_action' commands are
 reserved for the action of opening your extension's popups. They won't normally
 generate events that you can handle. If you need to take action based on your
 popup opening, consider listening for an 'onDomReady' event inside your popup's
 code.
 </p>
+
+<h2 id="usage">Scope</h2>
+<p>By default, Commands are scoped to the Chrome browser, which means that while
+the browser does not have focus, the shortcut will be inactive. On desktop
+Chrome, Commands can instead have global scope 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>
+
+<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
+to specifying only Ctrl+Shift+[0..9] as global shortcuts. This is to minimize
+the risk of overriding shortcuts in other applications since if, for example,
+Alt+P were to be allowed as global, the printing shortcut might not work in
+other applications.</p>
+
+<p>Example:</p>
+
+<pre data-filename="manifest.json">
+{
+  "name": "My extension",
+  ...
+  "commands": {
+    "toggle-feature-foo": {
+      "suggested_key": {
+        "default": "Ctrl+Shift+5"
+      },
+      "description": "Toggle feature foo",
+      <b>"global": true</b>
+    }
+  },
+  ...
+}</pre>