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Uses of those includes appear all over Blink. Consolidate all DEPS
include_rules regarding callbacks into third_party/blink/DEPS.

Change-Id: I83907a44a2409a7d24ccbdbaf084c6e9e9a3b795
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2213535
Commit-Queue: Henrique Ferreiro <hferreiro@igalia.com>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#772188}