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There is an option to configure the maximum size of the NetLog. The
default is 100MiB.

This is a re-land that was originally reviewed at https://chromium-review.googlesource.com/c/571514/

TBR=xunjieli@chromium.org

Bug: 679030
Change-Id: Ibf4fd80bca9ecd2d7899bc7039a930bbfc70ffa0
Reviewed-on: https://chromium-review.googlesource.com/580030Reviewed-by: Eric Roman <eroman@chromium.org>
Commit-Queue: Eric Roman <eroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488371}