Confirmed. Running a bisect.

Bisect result:

You are probably looking for a change made after 547247 (known good), but no later than 547248 (first known bad).
CHANGELOG URL:
The script might not always return single CL as suspect as some perf builds might get missing due to failure.
  https://chromium.googlesource.com/chromium/src/+log/e5d79e6c07b0280e81db5c2b5636b4d1d2511a02..090b1a4fea8bd71d2bd5e3503d3397985ad58022

[XHR] Replace usage of download_to_file with new download_to_blob feature.

download_to_file isn't really implementable with the network service (since
there is no central browser-side place where all fetches pass through), and
because we'd like blobs downloaded by XHR to be managed by the blob system
anyway, this replaces download_to_file with a new download_to_blob feature.

With this, blink::ResourceLoader redirects the datapipe it receives from a
URLLoader to the blob system, and passes the resulting blob back to XHR.

Design doc: https://docs.google.com/document/d/1V_rFqFeYc_XpzEc_hGF9Wlat5mH62lREJ1I1dCJ4lX0/edit#heading=h.2ndyupa99wqr

Bug:  754493 ,  712693 ,  791702 

Change-Id: I258150937c424b72824dadbc2832764ed54c1ca5
Reviewed-on: https://chromium-review.googlesource.com/955957
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547248}

Ah yes, a known issue I was hoping to get away with (since who would want to create large blobs right after startup...), but still definitely something we should fix. The problem here is that the blob system (in particular its ability to use the disk) is lazily initialized, and XHR-ing to a blob doesn't make sure initialization has happened.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/faea0bfbfb62ce9adac8e9d58adc1e6e689778aa

commit faea0bfbfb62ce9adac8e9d58adc1e6e689778aa
Author: Marijn Kruisselbrink <mek@chromium.org>
Date: Tue May 22 20:38:05 2018

[BlobStorage] Wait for limits calculation when deciding how to stream to blobs.

This makes sure that we don't incorrectly reject large XHR-to-blob
attempts before we've initialized blob storage limits.

Bug:  843975 
Change-Id: I93b45b020fea4a0964af0f26ff7337e4cf85d3d2
Reviewed-on: https://chromium-review.googlesource.com/1068116
Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#560760}
[modify] https://crrev.com/faea0bfbfb62ce9adac8e9d58adc1e6e689778aa/storage/browser/blob/blob_builder_from_stream.cc
[modify] https://crrev.com/faea0bfbfb62ce9adac8e9d58adc1e6e689778aa/storage/browser/blob/blob_builder_from_stream_unittest.cc
[modify] https://crrev.com/faea0bfbfb62ce9adac8e9d58adc1e6e689778aa/storage/browser/blob/blob_memory_controller.cc
[modify] https://crrev.com/faea0bfbfb62ce9adac8e9d58adc1e6e689778aa/storage/browser/blob/blob_memory_controller.h
[modify] https://crrev.com/faea0bfbfb62ce9adac8e9d58adc1e6e689778aa/storage/browser/blob/blob_registry_impl_unittest.cc

That should fix this for M68, don't think it's worth backporting to M67, since it only effects operations right after launching chrome.