Aria-hide the text content part of a MathML formula (bug 1998046)

It'll avoid to have the text content and the MathML content read by
screen readers.

test/integration/accessibility_spec.mjs

@@ -336,10 +336,20 @@ describe("accessibility", () => {
             expect(mathML)
               .withContext(`In ${browserName}`)
               .toEqual(
-                " <msqrt><msup><mi>x</mi><mn>2</mn></msup></msqrt> <mo>=</mo> <mrow><mo>|</mo><mi>x</mi><mo>|</mo></mrow> "
+                ` <msqrt><msup><mi>x</mi><mn>2</mn></msup></msqrt> <mo>=</mo> <mrow intent="absolute-value($x)"><mo>|</mo><mi arg="x">x</mi><mo>|</mo></mrow> `
               );
+
+            // Check that the math corresponding element is hidden in the text
+            // layer.
+            const ariaHidden = await page.$eval("span#p58R_mc13", el =>
+              el.getAttribute("aria-hidden")
+            );
+            expect(ariaHidden).withContext(`In ${browserName}`).toEqual("true");
           } else {
-            pending(`Sanitizer API (in ${browserName}) is not supported`);
+            // eslint-disable-next-line no-console
+            console.log(
+              `Pending in Chrome: Sanitizer API (in ${browserName}) is not supported`
+            );
           }
         })
       );
@@ -379,7 +389,10 @@ describe("accessibility", () => {
                 '<math display="block"> <msup> <mi>𝑛</mi> <mi>𝑝</mi> </msup> <mo lspace="0.278em" rspace="0.278em">=</mo> <mi>𝑛</mi> <mspace width="1.000em"></mspace> <mi> mod </mi> <mspace width="0.167em"></mspace> <mspace width="0.167em"></mspace> <mi>𝑝</mi> </math>'
               );
           } else {
-            pending(`Sanitizer API (in ${browserName}) is not supported`);
+            // eslint-disable-next-line no-console
+            console.log(
+              `Pending in Chrome: Sanitizer API (in ${browserName}) is not supported`
+            );
           }
         })
       );

web/struct_tree_layer_builder.js

@@ -341,6 +341,18 @@ class StructTreeLayerBuilder {
           element.setHTML(node.mathML, {
             sanitizer: MathMLSanitizer.sanitizer,
           });
+          // Hide all the corresponding content elements in the text layer in
+          // order to avoid screen readers reading both the MathML and the
+          // text content.
+          for (const { id } of node.children || []) {
+            if (!id) {
+              continue;
+            }
+            const elem = document.getElementById(id);
+            if (elem) {
+              elem.ariaHidden = true;
+            }
+          }
         }
         if (
           !node.mathML &&