Syntax errors in some extra tests

Some of the tests under https://www.khronos.org/registry/webgl/sdk/tests/extra fail with syntax errors:
#### "Uncaught SyntaxError: In strict mode code, functions can only be declared at toplevel or immediately within another function."
- https://www.khronos.org/registry/webgl/sdk/tests/extra/fbo-lost-context.html
- https://www.khronos.org/registry/webgl/sdk/tests/extra/out-of-memory.html
- https://www.khronos.org/registry/webgl/sdk/tests/extra/out-of-resources.html
- https://www.khronos.org/registry/webgl/sdk/tests/extra/out-of-vram.html
#### "Uncaught ReferenceError: canvas is not defined"
- https://www.khronos.org/registry/webgl/sdk/tests/extra/offscreen-issue.html

Open the five listed tests under tests/extra and reproduce the reported browser errors. Inspect the script sections in fbo-lost-context.html, out-of-memory.html, out-of-resources.html, out-of-vram.html, and offscreen-issue.html. Done means these tests load without the reported SyntaxError or ReferenceError.

Written by the indexing model from the issue text.