Use EnsureComputedStyle instead of StyleForElement in AX.

StyleForElement doesn't create ancestor computed styles as necessary to
do inheritance correctly. Noticed the listed TEST would trigger a sanity
DCHECK in StyleForElement() for another CL. Without this change we would
inherit styles from initial styles instead of the parent element.

TEST=accessibility/name-calc-visibility.html
TEST=inspector-protocol/accessibility/accessibility-nameSources-visiblity.js

Change-Id: Icd6d669b0ff04f97fcdd637530f56619e8b1f3f0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1789233Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#694481}

third_party/blink/renderer/modules/accessibility/ax_object.cc

@@ -1605,8 +1605,7 @@ bool AXObject::IsHiddenForTextAlternativeCalculation() const {
   if (Node* node = GetNode()) {
     auto* element = DynamicTo<Element>(node);
     if (element && node->isConnected()) {
-      scoped_refptr<ComputedStyle> style =
-          document->EnsureStyleResolver().StyleForElement(element);
+      const ComputedStyle* style = element->EnsureComputedStyle();
       return style->Display() == EDisplay::kNone ||
              style->Visibility() != EVisibility::kVisible;
     }