May have a clue:

$ python tools/bisect-builds.py -a linux64 -g 599034 -b 620241 --use-local-cache -- --no-first-run --user-data-dir=/tmp/xsofjeoifj https://source.android.com
...
You are probably looking for a change made after 618448 (known good), but no later than 618452 (first known bad).
https://chromium.googlesource.com/chromium/src/+log/d871491cd5b7fe019d9cb7a6e578f8bbdf8fb8fd..68bf6651c739bec574bf33b5b4bce21e0316ce5f

Suspecting https://chromium.googlesource.com/chromium/src/+/90070dcbb75bf7065f86f4705438380a295f2f65 which landed in 73.0.3648.0.

When I revert that CL the page loads again. yhirano@ can we revert this change before 73 branch cut?

Fine.

Thanks, revert started at https://chromium-review.googlesource.com/c/chromium/src/+/1401925

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/83624e506109545f02ce6ce8437bd4c0d64af34f

commit 83624e506109545f02ce6ce8437bd4c0d64af34f
Author: Matt Falkenhagen <falken@chromium.org>
Date: Wed Jan 09 05:46:41 2019

Revert "Introduce BufferingBytesConsumer"

This reverts commit 90070dcbb75bf7065f86f4705438380a295f2f65.

Reason for revert: Breaks loading at least one site, see  https://crbug.com/920066 

Original change's description:
> Introduce BufferingBytesConsumer
>
> The fetch spec requires us to relieve backpressure when updating the
> HTTPS cache. This has been implemented in content/renderer/loader as
> SharedMemoryDataConsumerHandle::BackpressureMode, but this CL moves the
> implementation to blink/renderer/core/fetch in order to deprecate
> WebDataConsumerHandle.
>
> Bug: 911036
> Change-Id: Ia0161a7c5f1dbd17a994c11865cf035816235bb0
> Reviewed-on: https://chromium-review.googlesource.com/c/1364972
> Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
> Reviewed-by: Makoto Shimazu <shimazu@chromium.org>
> Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#618449}

TBR=yhirano@chromium.org,kouhei@chromium.org,shimazu@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 911036,  920066 
Change-Id: I332e52a8a75936ac8dff547bd7dd76cbcd69ca5c
Reviewed-on: https://chromium-review.googlesource.com/c/1401925
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621055}
[modify] https://crrev.com/83624e506109545f02ce6ce8437bd4c0d64af34f/content/renderer/loader/shared_memory_data_consumer_handle.cc
[modify] https://crrev.com/83624e506109545f02ce6ce8437bd4c0d64af34f/content/renderer/loader/shared_memory_data_consumer_handle.h
[modify] https://crrev.com/83624e506109545f02ce6ce8437bd4c0d64af34f/content/renderer/loader/shared_memory_data_consumer_handle_unittest.cc
[modify] https://crrev.com/83624e506109545f02ce6ce8437bd4c0d64af34f/content/renderer/loader/web_url_loader_impl.cc
[modify] https://crrev.com/83624e506109545f02ce6ce8437bd4c0d64af34f/third_party/blink/renderer/core/BUILD.gn
[modify] https://crrev.com/83624e506109545f02ce6ce8437bd4c0d64af34f/third_party/blink/renderer/core/fetch/BUILD.gn
[delete] https://crrev.com/91e17c7ef3afbcab7a3caa72d2c166cfc20585de/third_party/blink/renderer/core/fetch/buffering_bytes_consumer.cc
[delete] https://crrev.com/91e17c7ef3afbcab7a3caa72d2c166cfc20585de/third_party/blink/renderer/core/fetch/buffering_bytes_consumer.h
[delete] https://crrev.com/91e17c7ef3afbcab7a3caa72d2c166cfc20585de/third_party/blink/renderer/core/fetch/buffering_bytes_consumer_test.cc
[modify] https://crrev.com/83624e506109545f02ce6ce8437bd4c0d64af34f/third_party/blink/renderer/core/fetch/fetch_manager.cc

This should be fixed in the next canary with the CL, please reopen if not.