Per guidance from the the SwiftShader project, the OpenGL backend in SwiftShader will no longer be supported. Flutter uses OpenGL on SwiftShader in all its unit-test harnesses.

The recommendation is now to use Vulkan from SwiftShader with an OpenGL implementation sitting on top of it. Once such implementation exists in ANGLE.

Flutter has a dependency on ANGLE that is mainly used on Windows. To stick with the recommended directions of use, Flutter can update both DEPS and reconfigure GN rules for the test harness to use ANGLE OpenGL on SwiftShader Vulkan. There should be no code changes necessary.