GitLab

Adds throttling that pauses loading when too much unread data
accumulates, then resumes loading when the backlog clears.

For consistency, switches all EXPECT_CALL() expectations without
argument matchers in url_loader_unittest.cc to the argument-less form.

Fixed: 1099022
Change-Id: Iac02f17bbcac166e92e19611e5ad35786a3c3a2f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2427844
Commit-Queue: K. Moon <kmoon@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#810369}