Chrome extension using sidebar
I was looking for a sidebar solution as well and ended up at Implement chrome.sidebar API thread.
According to the Sidebar PRD, it is already possible to create sidebar by:
- injecting a script into the page which edits the HTML of the page to display a sidebar by modifying the DOM to insert an iframe which loads the contents of the sidebar from a remote server.
- the injected script can edit the DOM directly to display a sidebar, the contents of which are passed via message.
However, there are many downsides (explained in the same document) with regard to:
Usability, Performance, Security, Privacy (Extension sniffing as well as Third party cookies) and Accessibility.
You can watch a demo of what they are preparing for future Sidebar Component.
It might help in shipping the feature quicker if you star the thread.
update
Per this comment, Chrome will not get a built-in sidebar component.
The problem is that you are opening, theoretically, the sidebar inside your popup, not in the current page.
You should add a content script in the page, with a function that opens the sidebar. So, in your popup you should just retrieve the current tab then call this function from it.
Also, as Boris Smus said in your question, sidebars will be discontinued in future versions. So I advice you to create your own sidebar frame via content scripts.
Update
To help you, I've made a simple extension that create a sidebar on current page.
@Curtis hosted my sample extension on Github, you can clone it here.