Here is the URL for Google Chrome Dev Channel offline installer. Or try the links on this page.
Since the above links are often not up to date, check the following answer, which contains direct links to particular binary releases. Basically, to download the latest versions manually, the download link pattern is this:
release notes blog. The actual URL of the latest update version can also be seen using Fiddler and trying out the Google Chrome update through the browser.
The link to Dev channel updates stream is here.