Unassigning from myself - I may still tackle the SSL buffer one, and the idle sockets one, but I think we've proven there's a good chance I won't have time for too much this stuff.

Linking  Issue 671420  here, so other folks can stay up to date. Short summary is that X509* is going away (together with its hundreds of small allocations). It is going to be replaced with CRYPTO_BUFFER. According to davidben@'s initial investigation, it should improve net/cert/ memory usage by 4x. See more details in the linked crbug. Thanks David and the boringssl team for the great work.

Is there still active progress on this?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a46c80057c897f53772701bbde45b551401b691e

commit a46c80057c897f53772701bbde45b551401b691e
Author: Helen Li <xunjieli@chromium.org>
Date: Thu Sep 21 21:57:32 2017

Deprecate Net.Socket.IdleSocketFate histogram

Idle socket reuse rate is high on Desktop (close to 50%) and on Mobile (~30% on
Android). Newer memory instrumentation data do not show socket pool as a hotspot. 
There have been a few projects to reduce the amount of memory an idle socket
retains (e.g. use CRYPTO_BUFFER  Issue 671420  and lazy buffer initialization
 Issue 524258 ).

I do not have any follow-up experiments that would use this histogram, so I am
removing it. The histogram was added in crrev.com/2450463002.

BUG:  620852 
Change-Id: I1a7f858bfcafbcaad708366fa4d2bd5e967e14b0
Reviewed-on: https://chromium-review.googlesource.com/673272
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Commit-Queue: Helen Li <xunjieli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#503576}
[modify] https://crrev.com/a46c80057c897f53772701bbde45b551401b691e/net/socket/client_socket_pool_base.cc
[modify] https://crrev.com/a46c80057c897f53772701bbde45b551401b691e/net/socket/client_socket_pool_base_unittest.cc
[modify] https://crrev.com/a46c80057c897f53772701bbde45b551401b691e/tools/metrics/histograms/enums.xml
[modify] https://crrev.com/a46c80057c897f53772701bbde45b551401b691e/tools/metrics/histograms/histograms.xml

All linked bugs are closed. I am archiving this metabug as there's no active development on this issue for a while now.