Chromium build failed on Gentoo – fixed

This is where it started
localhost ~ # grep "error:" /var/tmp/portage/www-client/chromium-74.0.3729.169/temp/build.log
[3419/16611] python ../../mojo/public/tools/bindings/generate_type_mappings.py --output gen/services/viz/privileged/interfaces/gl/gl__type_mappings --dependency gen/gpu/ipc/common/interfaces__type_mappings --dependency gen/media/mojo/interfaces/interfaces__type_mappings --dependency gen/ui/gfx/geometry/mojo/mojo__type_mappings --dependency gen/ui/gfx/mojo/mojo__type_mappings --dependency gen/url/mojom/url_mojom_gurl__type_mappings --start-typemap public_headers=//gpu/command_buffer/common/constants.h traits_headers=//services/viz/privileged/cpp/context_lost_reason_traits.h type_mappings=viz.mojom.ContextLostReason=gpu::error::ContextLostReason
x86_64-pc-linux-gnu-g++: fatal error: Killed signal terminated program cc1plus
localhost ~ #
localhost ~ # dmesg |grep cc1plus
[20473.830849] [ 28321] 250 28321 564527 228755 4042752 258622 0 cc1plus
[20473.830857] [ 28357] 250 28357 409737 144997 2793472 184788 0 cc1plus
[20473.830866] [ 28372] 250 28372 379021 235063 2592768 69175 0 cc1plus
[20473.830874] [ 28375] 250 28375 405111 298734 2744320 26004 0 cc1plus
[20473.830884] Out of memory: Kill process 28321 (cc1plus) score 237 or sacrifice child
[20473.830888] Killed process 28321 (cc1plus) total-vm:2258108kB, anon-rss:915020kB, file-rss:0kB, shmem-rss:0kB
[20473.960229] oom_reaper: reaped process 28321 (cc1plus), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
[39359.986750] cc1plus invoked oom-killer: gfp_mask=0x6200ca(GFP_HIGHUSER_MOVABLE), nodemask=(null), order=0, oom_score_adj=0
[39359.986750] cc1plus cpuset=/ mems_allowed=0
[39359.986750] CPU: 1 PID: 13930 Comm: cc1plus Tainted: G OE 4.19.44-gentoo #1
[39359.986751] [ 13918] 250 13918 527207 216835 3739648 232411 0 cc1plus
[39359.986751] [ 13930] 250 13930 449644 182289 3117056 187980 0 cc1plus
[39359.986751] [ 13939] 250 13939 383355 270389 2637824 40695 0 cc1plus
[39359.986751] [ 13942] 250 13942 397893 279494 2682880 35731 0 cc1plus
[39359.986751] Out of memory: Kill process 13918 (cc1plus) score 218 or sacrifice child
[39359.986751] Killed process 13918 (cc1plus) total-vm:2108828kB, anon-rss:867336kB, file-rss:4kB, shmem-rss:0kB
[39360.059949] oom_reaper: reaped process 13918 (cc1plus), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
localhost ~ #
Source compiled.
Test phase [not enabled]: www-client/chromium-74.0.3729.169
Install chromium-74.0.3729.169 into /var/tmp/portage/www-client/chromium-74.0.3729.169/image category www-client
/var/tmp/portage/www-client/chromium-74.0.3729.169/work/chromium-74.0.3729.169
Completed installing chromium-74.0.3729.169 into /var/tmp/portage/www-client/chromium-74.0.3729.169/image
Final size of build directory: 6666072 KiB ( 6.3 GiB)
Final size of installed tree: 456428 KiB (445.7 MiB)