Chrome Version: All
OS: All

What steps will reproduce the problem?
(1) Open a fresh Incognito window.
(2) Visit https://cloud3squared.com/files/sw-analytics-demo/index.html (or any other PWA that stores data using the Cache Storage API).
(3) Observe that there is only ~120mb of storage quota (https://developers.google.com/web/updates/2017/08/estimating-available-storage-space) allocated to each origin in that window.
(4) Compare with a non-Incognito window, which is allocated a storage quota proportional to the amount of free space left on the device.
(5) Reload a few times and the quota will be quickly used up.

What is the expected result?
Something larger than ~120mb—ideally the same quota as a non-Incognito window would get, so that developers testing their Progressive Web Apps in Incognito windows don't see an artificially low limit.

What happens instead?
The ~120mb is very easy to use up, leading to QuotaExceeded exceptions that would likely not be seen in non-Incognito windows (unless the device was legitimately storage constrained).

The fact that opaque cached responses contribute ~7mb each to the storage usage means that you can cache around 17 entries before your entire PWA stops allowing additional caching.

(See https://bugs.chromium.org/p/chromium/issues/detail?id=796060 for more context as to why the quota is being used so quickly.)