Currently desktop ChromeOS and builders build Chrome using Precise sysroot, while regular ChromeOS builds use custom sysroots.

The custom Precise sysroot was originally added since Wheezy chroot had a different set of dependencies.

The problem with Precise chroot is that it has old packages and it can't easily be updated to newer ones.
libdrm-dev for example doesn't contain any new atomic interface.
This makes it hard to land and compile code Chromium code that depends on newer libraries.

crrev.com/2594483002 adds libdrm to third party (similar to what we do with minigbm) and also contains more details on other options tried: https://codereview.chromium.org/2594483002#msg9

This means with crrev.com/2594483002 we have one libdrm in third_party, one in cros, and one in the sysroot.
We tried to remove libdrm from the sysroot, but other packages in the sysroot (i.e: libwayland-egl) depends on libdrm-dev.

This bug is to track the issue and to try to come up with something better than the current situation.