For example, imagine I wanted to write a test that shows the following bug: #126673.

I'd (as far as I understand it) have to write this in the framework layer (flutter/flutter) in order to get full tooling support, and in the case of validating that we're drawing the "right kind of lines", probably golden-file tests. Within flutter/engine, there are two other kinds of tests that don't seem to meet my needs:

1. aiks_unittests.cc, which runs on the Impeller backend with a custom harness, but doesn't let me reuse existing tests and will be harder to catch Skia <> Impeller fidelity issues.
2. canvas_test.dart, which only runs on the software backend (which Impeller doesn't support if I understand correctly).

Related issues:

• Support golden tests in C++ unit tests for the engine #53784
• Wire up pixel tests via Skia Gold for dart:ui test harness in the engine. #76565