Redirecting URL in a chrome extension

Question

How can I go about redirecting chrome in an extension when visiting a given URL?

For example: when I visit http://yahoo.com/ I want it to redirect to http://google.com/

NOTE: A former version of this question asked whether there is any Google chrome extension which automatically redirects the tab when it visits a certain URL. Accordingly, the (currently two) answers below address different questions.

Answer 1

There are many options, the one more convoluted than the other.

1. The webRequest API, specifically the onBeforeRequest event. (Even better, the upcoming declarativeWebRequest API).
2. Content scripts. Inject location.replace('http://example.com') in a page.
3. The tabs API. Use the onUpdated event to detect when a page has changed its location, and chrome.tabs.update to change its URL. Avoid an infinite loop though!

The first one is the best one, because it is activated before a page is even requested. The second one can be activated after the request has been fulfilled, but before the page is rendered ("run_at":"document_start") or after it's rendered ("run_at":"document_end"). I mentioned the last one for completeness, but you shouldn't use it, because the other options are way better.

Here's an example using the webRequest API, a simple extension which allows me to browse pages on the Pirate bay, even though the main hosts are taken down by my ISP (the actual list of URLs is much longer, but I have omitted them for the sake of the example).
See match patterns for an explanation on the URL formats.

manifest.json

{
  "name": "The Pirate Bay",
  "description": "Redirect The Pirate Bay to a different host",
  "version": "1.0",
  "manifest_version": 2,
  "background": {"scripts":["background.js"]},
  "permissions": [
    "webRequest",
    "*://thepiratebay.se/*",
    "*://www.thepiratebay.se/*",
    "webRequestBlocking"
  ]
}

background.js

var host = "http://tpb.pirateparty.org.uk";
chrome.webRequest.onBeforeRequest.addListener(
    function(details) {
         return {redirectUrl: host + details.url.match(/^https?:\/\/[^\/]+([\S\s]*)/)[1]};
    },
    {
        urls: [
            "*://piratebay.se/*",
            "*://www.piratebay.se/*"
        ],
        types: ["main_frame", "sub_frame", "stylesheet", "script", "image", "object", "xmlhttprequest", "other"]
    },
    ["blocking"]
);