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From the dev/beta/stable experiments, this reduces memory by multiple
MiB per renderer @95th percentile, with larger savings on popular
websites (7MiB on Facebook at the median on desktop, for instance).

Enable it by default.

Bug: 1029320
Change-Id: Iaa355d50f80617b2a8eb763984761a5cc3d5aae3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2410041Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Benoit L <lizeb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807418}