Add reftests: canvas display after device lost

[perryuwang]

Issue: #3251

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Requirements for PR author:

• All missing test coverage is tracked with "TODO" or .unimplemented().
• New helpers are /** documented */ and new helper files are found in helper_index.txt.
• Test behaves as expected in a WebGPU implementation. (If not passing, explain above.)
• Test have be tested with compatibility mode validation enabled and behave as expected. (If not passing, explain above.)

Requirements for reviewer sign-off:

• Tests are properly located in the test tree.
• Test descriptions allow a reader to "read only the test plans and evaluate coverage completeness", and accurately reflect the test code.
• Tests provide complete coverage (including validation control cases). Missing coverage MUST be covered by TODOs.
• Helpers and types promote readability and maintainability.

When landing this PR, be sure to make any necessary issue status updates.

[kainino0x]

LGTM; please review the commit I pushed on the end!

[kainino0x]

This will reconfigure the canvas between device.destroy() and ctx.getCurrentTexture(). This could interact with the test. I pushed a commit which adds 4 more cases that draw without reconfiguring - please review to make sure the expected results look right.

[perryuwang]

I think cvs10 should display transparent color.

[kainino0x]

Hm, why is that? I think the spec says, reconfiguring should Replace the drawing buffer (which sets the drawing buffer to transparent black), then when the canvas is presented, get a copy of the image contents of a context clears the alpha to 0.

[perryuwang]

My understanding is that although reconfiguring has set the drawing buffer to black, but drawAfterLoss is false(getCurrentTexture() is not called), canvas is not redrawn and it is no content to presented, so it should be transparent.
For cvs11, because drawAfterLost is true, it should be displayed in black.

[kainino0x]

According to the spec, configure() also replaces the drawing buffer with a blank image (as do context creation, resize, unconfigure(), getCurrentTexture(), and transferToImageBitmap()).

Which makes me realize there should probably be some tests for unconfigure as well. I was going to add some but didn't think of why it would be useful.

[kainino0x]

Let me remove my change from the end and open a new PR for the extra tests I want to add.