This CL avoids the head-allocations done in a sum of the squared values
in a nested vector.
Bug: webrtc:11361, chromium:1052086
Change-Id: I698b855bdd54df2147ef3b6d5e3d401401228d76
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/168543
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30520}