Introduce a new 'all_frames' property to content scripts and

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

 <div id="pageData-title" class="pageData">Content Scripts</div>
 <div id="pageData-showTOC" class="pageData">true</div>
 
 <p>
 Content scripts are JavaScript files that run in the context of web pages.
 By using the standard
 <a href="http://www.w3.org/TR/DOM-Level-2-HTML/">Document
 Object Model</a> (DOM),
 they can read details of the web pages the browser visits,
 or make changes to them.
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     <br><br>
 
     In the case of <code>"document_idle"</code>, the browser chooses a time to inject scripts between <code>"document_end"</code> and immediately after the <code><a href="http://www.whatwg.org/specs/web-apps/current-work/#handler-onload">window.onload</a></code> event fires. The exact moment of injection depends on how complex the document is and how long it is taking to load, and is optimized for page load speed.
 
     <br><br>
 
     <b>NOTE:</b> In <code>document_idle</code>, content scripts may not necessarily receive the window.onload event, because they may run after it has
     already fired. In most cases, listening for the onload event is unnecessary for content scripts running at <code>document_idle</code> because they are guaranteed to run after the DOM is complete. If your script definitely needs to run after <code>window.onload</code> you can check if it has already fired by using the <code><a href="http://www.whatwg.org/specs/web-apps/current-work/#dom-document-readystate">document.readyState</a></code> property.</td>
   </tr>
+  <tr>
+    <td>all_frames</td>
+    <td>boolean</td>
+    <td><em>Optional.</em>
+    Controls whether the content script runs in all frames of the matching page, or only the top frame.
+    <br><br>
+    Defaults to <code>false</code>, meaning that only the top frame is matched.</td>
+  </tr>
 </table>
 
 
 <h2 id="execution-environment">Execution environment</h2>
 
 <p>Content scripts execute in a special environment called an <em>isolated world</em>. They have access to the DOM of the page they are injected into, but not to any JavaScript variables or functions created by the page. It looks to each content script as if there is no other JavaScript executing on the page it is running on. The same is true in reverse: JavaScript running on the page cannot call any functions or access any variables defined by content scripts.
 
 <p>For example, consider this simple page:
 
 <pre>hello.html
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 just like you would any other URL,
 as the following code shows.
 </p>
 
 
 <pre>
 <em>//Code for displaying &lt;extensionDir>/images/myimage.png:</em>
 var imgURL = <b>chrome.extension.getURL("images/myimage.png")</b>;
 document.getElementById("someImage").src = imgURL;
 </pre>