Optimize disabling ARB_texture_rectangle In https://crrev.com/c/1838418 I added the ability to disable ARB_texture_rectangle so that we can use it in the WebGL implementation but disable it when compiling user shaders. Unfortunately disabling and re-enabling the extension causes the shader translator to be reinitialized which turns out to be more expensive than the actual work of shader translation, at least for small shaders. It's slow enough to cause timeouts in WebKit's WebGL conformance test runs. This introduces an alternate method of disabling ARB_texture_rectangle in the translator which is much faster because it avoids reinitializing the translator. Bug: angleproject:3956 Change-Id: I5d31b683ff19a59bdfd289cfd3c609f64ef5e25b Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1991969 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: James Darpinian <jdarpinian@chromium.org>