Extensions: Do not skip content verification on contiguous seek of a resource load.

With network service, all extension resource load that is greater than 1k
bytes in size generate OnSeekComplete notification. The existing code we
had around this before network service assumed the seek won't be contiguous
and would reset/nuke ContentVerifyJob in that case.

This CL allows ContentVerifyJob to continue to run if OnSeekComplete was
triggered that was result of a contiguous seek.

This CL also adds a regression test for this issue.

Bug: 964043
Change-Id: Ib9df8bd818fb8dd3abb4f48bf80d8eda6216f04b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1615434
Commit-Queue: Istiaque Ahmed <lazyboy@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Chris Mumford <cmumford@google.com>
Cr-Commit-Position: refs/heads/master@{#661459}
4 files changed