blink/bindings: Add (de)compression histograms for ParkableString.

Records the size, latency and throughput of parkable strings at compression and
decompression time. As these values are correlated, recording separate
histograms is necessary, and as not all compressed strings are decompressed,
separate histograms for compression and decompression are required.

Bug: 877044
Change-Id: Iec53e6d4f249e109165b0b3be6e2e245fc2bfd40
Reviewed-on: https://chromium-review.googlesource.com/c/1307440
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Benoit L <lizeb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605296}
3 files changed