Разработчики chromium без дела не сидят.

>>> Running pre-merge checks for www-client/chromium-56.0.2924.76-r1
* Checking for at least 16 GiB RAM ...                                             
* There is NOT at least 16 GiB RAM

* Space constraints set in the ebuild were not met!
* The build will most probably fail, you should enhance the space
* as per failed tests.