The tabs have been changed from Chrome and Chromium v. 50 to v. 51. In version 51, Google has implemented Material Design by default, which has a more Safari'ish look. It is up for debate which one is better looking.
To disable it, go to
chrome://flags in chrome and chromium and search for
material design. You should come up with an option that says something like "Material Design in the browser's top." Select from the drop-down "Non-material" and restart the browser.
Unfortunately, in version 51 of Chrome and Chromium on Ubuntu, there appears to be bug that does not allow you to disable it straight from the browser. It appears that it will, however, be fixed in v. 53.
You can disable Material Design in Chromium version 51 by running it from the terminal with the material design flag:
...and if you want it to do that by default, simply search for the line in
/usr/share/applications/chromium-browser.desktop that begins with
Exec=[...] and add the
--top-chrome-md=non-material right after