[Bug]: dpi='figure' option no longer working in savefig #26252

Bug summary

The default dpi='figure' option in savefig no longer appears to work correctly - instead the DPI is a fixed value.

Code for reproduction

import matplotlib.pyplot as plt

fig = plt.figure()
fig.set_dpi(10)
ax = fig.add_subplot(1, 1, 1)
fig.savefig("test_dpi.png", dpi="figure")

Actual outcome

A 100 DPI figure:

Expected outcome

A 10 DPI figure:

Additional information

I bisected this and it appears to have been introduced in #19126 - prior to this, it worked fine.

Operating system

All platforms

Matplotlib Version

Bug first appeared in Matplotlib 3.5

Matplotlib Backend

MacOS X and Agg

Python version

3.11 but seen in other Python versions

Jupyter version

No response

Installation

pip