Auto merge of #9911 - magni-:dont_use_lookup_tables, r=michaelwu

Do not use lookup tables for put_image_data

Fixes #9599

"This is the first Rust code I have ever written" (and also my first time writing real browser code, it's been quite the learning experience).

Some questions:

> For really fast CPU results, use integer SIMD instructions to handle more than one pixel at a time.

This was out of the scope of #9599, right? I started looking into doing that, but it seems to be a lot more work than the `E-easy` label would suggest. [`std::simd`](https://doc.rust-lang.org/1.0.0/std/simd/index.html) is marked as "unstable", is that a blocker?

> 128 can be added before dividing to round more accurately.

@michaelwu, what did you mean by that?

Also, the #9599 is `Do not use lookup tables for {Get,Put}ImageData operations`, but we only use lookup tables for the `Put`, not the `Get`, right?

Sorry for all the noobish questions.

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tests/wpt/metadata/2dcontext/pixel-manipulation/2d.imageData.put.unchanged.html.ini

@@ -0,0 +1,5 @@
+[2d.imageData.put.unchanged.html]
+  type: testharness
+  [putImageData(getImageData(...), ...) has no effect]
+    expected: FAIL
+