I've only seen a couple of failures so far. The first one being build #5721. Here's a link to the builds:
https://build.chromium.org/p/chromium.gpu.fyi/builders/Mac%20Retina%20Release%20%28NVIDIA%29/builds/5721
https://build.chromium.org/p/chromium.gpu.fyi/builders/Mac%20Retina%20Release%20%28NVIDIA%29/builds/5750

Looking at the log from the failure, there's a couple of clear error logs from the gl decoder:

[5817:775:1022/171855.938839:ERROR:gles2_cmd_decoder.cc(18119)] [.DisplayCompositor-0x7f8e66828e00]GL ERROR :GL_INVALID_OPERATION : glCreateAndConsumeTextureCHROMIUM: invalid mailbox name
[5817:775:1022/171855.940051:ERROR:gles2_cmd_decoder.cc(9938)] [.DisplayCompositor-0x7f8e66828e00]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering.
[5817:775:1022/171855.951518:ERROR:gles2_cmd_decoder.cc(9938)] [.DisplayCompositor-0x7f8e66828e00]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering.

+xlai, in case this makes the error obvious.