Reland "Expose visibility-hidden elements"

This was reverted here:
https://chromium-review.googlesource.com/c/chromium/src/+/1692384
due to failure on failure on linux-chromeos-rel
ChromeVoxPanelTest.LinkMenu

As of https://chromium-review.googlesource.com/c/chromium/src/+/1708415
This test no longer fails.

Original CL:
https://chromium-review.googlesource.com/c/chromium/src/+/1646877

Original Change description:
> Expose visibility-hidden elements
>
> This change allows visibility-hidden elements to be returned from
> UIA_DescribedByPropertyId and UIA_LabeledByPropertyId. To allow for
> this, visibility-hidden elements had to be exposed to the AX tree.
> This change can be observed in the update to
> AXObject::ComputeAccessibilityIsIgnoredPassThrough().
>
> Given:
> <div id="a" aria-label="foo" style="visibility:hidden"> </div>
> <div id="b" aria-labelled-by="a"> </div>
>
> When doing TextAlternative calculation for b, we know we are
> "in_aria_labelled_by_traversal", therefore we do not check to see
> if the node "IsHiddenForTextAlternativeCalculation", therefore
> correctly calculating the name for node "b".
> But, when we are doing TextAlternative calculation for node "a",
> we do not know if node "a" is the target of aria-labelledby, and
> is not considered to be "in_aria_labelled_by_traversal", so the
> name is an empty string: "".
> This is an issue, as the UIA_LabeledByPropertyId on node "b"
> returns node "a", and node "a" has an incorrect name of empty
> string.
>
> For purposes of computing a non-recursive text alternative,
> if an ignored and IsHiddenForTextAlternativeCalculation node
> is included in the tree, assume that it is the target of
> aria-labelledby or aria-describedby, since we can't tell
> yet whether that's the case. If it isn't exposed, the AT
> will never see the name anyways.
>
> This new behavior is only applied when calculating the
> TextAlternative for the ignored node directly, not in the
> recursive case. This ensures this new behavior is only applied
> to the ignored node, and does not influence the name calculation
> of other nodes.

Bug: 651614
Change-Id: I6ec57cbd36606890eaf1fd4e72d8442cae2442ad
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1730851Reviewed-by: Kevin Babbitt <kbabbitt@microsoft.com>
Reviewed-by: Alice Boxhall <aboxhall@chromium.org>
Commit-Queue: Jacques Newman <janewman@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#683439}

content/browser/accessibility/dump_accessibility_tree_browsertest.cc

@@ -1309,6 +1309,20 @@ IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest, AccessibilityHeading) {
   RunHtmlTest(FILE_PATH_LITERAL("heading.html"));
 }
 
+IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest, AccessibilityHidden) {
+  RunAriaTest(FILE_PATH_LITERAL("hidden.html"));
+}
+
+IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest,
+                       AccessibilityHiddenDescribedBy) {
+  RunAriaTest(FILE_PATH_LITERAL("hidden-described-by.html"));
+}
+
+IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest,
+                       AccessibilityHiddenLabeledBy) {
+  RunAriaTest(FILE_PATH_LITERAL("hidden-labelled-by.html"));
+}
+
 IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest, AccessibilityHR) {
   RunHtmlTest(FILE_PATH_LITERAL("hr.html"));
 }

content/renderer/accessibility/blink_ax_tree_source.cc

@@ -1221,6 +1221,11 @@ void BlinkAXTreeSource::AddImageAnnotations(blink::WebAXObject& src,
   if (!base::FeatureList::IsEnabled(features::kExperimentalAccessibilityLabels))
     return;
 
+  // Reject ignored objects
+  if (src.AccessibilityIsIgnored()) {
+    return;
+  }
+
   // Reject images that are explicitly empty, or that have a name already.
   //
   // In the future, we may annotate some images that have a name

content/test/data/accessibility/aria/hidden-described-by-expected-blink.txt

+rootWebArea
+++genericContainer ignored
+++++genericContainer ignored
+++++++genericContainer ignored name='span-A1'
+++++++++staticText ignored
+++++++++genericContainer ignored name='span-A2'
+++++++++staticText ignored
+++++++++genericContainer description='span-A4' name='span-A3' descriptionFrom=relatedElement describedbyIds=genericContainer
+++++++++++genericContainer ignored name='span-A4'
+++++++++staticText ignored
+++++++genericContainer description='span-A2' name='span-B' descriptionFrom=relatedElement describedbyIds=genericContainer
+++++++genericContainer name='span-C'

content/test/data/accessibility/aria/hidden-described-by-expected-uia-win.txt

+document
+++group Name='span-A3' DescribedBy='span-A4'
+++group Name='span-B' DescribedBy='span-A2'
+++group Name='span-C'

content/test/data/accessibility/aria/hidden-described-by-expected-win.txt

+ROLE_SYSTEM_DOCUMENT READONLY FOCUSABLE
+++IA2_ROLE_SECTION name='span-A3' description='span-A4'
+++IA2_ROLE_SECTION name='span-B' description='span-A2'
+++IA2_ROLE_SECTION name='span-C'

content/test/data/accessibility/aria/hidden-described-by.html

+<!--
+@UIA-WIN-ALLOW:Descr*
+@BLINK-ALLOW:descr*
+@WIN-ALLOW:descr*
+-->
+<!DOCTYPE html>
+<html>
+<style>
+  .hide {
+    visibility: hidden;
+  }
+  .visible {
+    visibility: visible;
+  }
+</style>
+<body>
+  <div>
+    <span class="hide" aria-label="span-A1">
+      <span aria-label="span-A2" id="a2"></span>
+      <span class="visible" aria-label="span-A3" aria-describedby="a4">
+        <span class="hide" aria-label="span-A4" id="a4"></span>
+      </span>
+    </span>
+
+    <span aria-label="span-B" aria-describedby="a2"></span>
+    <span aria-label="span-C"></span>
+  </div>
+</body>
+</html>

content/test/data/accessibility/aria/hidden-expected-blink.txt

+rootWebArea
+++genericContainer ignored
+++++genericContainer ignored
+++++++genericContainer ignored name='a1'
+++++++++staticText ignored
+++++++++genericContainer ignored name='a2'
+++++++++staticText ignored
+++++++genericContainer name='b'
+++++++genericContainer name='c'

content/test/data/accessibility/aria/hidden-expected-uia-win.txt

+document
+++group Name='b'
+++group Name='c'

content/test/data/accessibility/aria/hidden-expected-win.txt

+ROLE_SYSTEM_DOCUMENT READONLY FOCUSABLE
+++IA2_ROLE_SECTION name='b'
+++IA2_ROLE_SECTION name='c'

content/test/data/accessibility/aria/hidden-labelled-by-expected-blink.txt

+rootWebArea
+++genericContainer ignored
+++++genericContainer ignored
+++++++genericContainer ignored name='span-A1'
+++++++genericContainer name='span-A2'
+++++++genericContainer name='span-A4' labelledbyIds=genericContainer
+++++++++genericContainer ignored name='span-A4'
+++++++genericContainer name='span-A2' labelledbyIds=genericContainer
+++++++genericContainer name='span-C'

content/test/data/accessibility/aria/hidden-labelled-by-expected-uia-win.txt

+document
+++group Name='span-A2'
+++group Name='span-A4' LabeledBy='span-A4'
+++group Name='span-A2' LabeledBy='span-A2'
+++group Name='span-C'

content/test/data/accessibility/aria/hidden-labelled-by-expected-win.txt

+ROLE_SYSTEM_DOCUMENT READONLY FOCUSABLE
+++IA2_ROLE_SECTION name='span-A2'
+++IA2_ROLE_SECTION name='span-A4'
+++IA2_ROLE_SECTION name='span-A2'
+++IA2_ROLE_SECTION name='span-C'

content/test/data/accessibility/aria/hidden-labelled-by.html

+<!--
+@UIA-WIN-ALLOW:Label*
+@BLINK-ALLOW:label*
+@WIN-ALLOW:label*
+-->
+<!DOCTYPE html>
+<html>
+<style>
+  .hide {
+    visibility: hidden;
+  }
+  .visible {
+    visibility: visible;
+  }
+</style>
+<body>
+  <div>
+    <span class="hide" aria-label="span-A1"></span>
+      <span aria-label="span-A2" id="a2"></span>
+      <span class="visible" aria-label="span-A3" aria-labelledby="a4">
+        <span class="hide" aria-label="span-A4" id="a4"></span>
+      </span>
+    </span>
+
+    <span aria-label="span-B" aria-labelledby="a2"></span>
+    <span aria-label="span-C"></span>
+  </div>
+</body>
+</html>

content/test/data/accessibility/aria/hidden.html

+<!DOCTYPE html>
+<html>
+<style>
+  .hide {
+    visibility: hidden;
+  }
+</style>
+<body>
+  <div>
+    <span class="hide" aria-label="a1">
+      <span aria-label="a2"></span>
+    </span>
+
+    <span aria-label="b"></span>
+    <span aria-label="c"></span>
+  </div>
+</body>
+</html>

content/test/data/accessibility/event/css-visibility-expected-win.txt

-EVENT_OBJECT_HIDE on <div.a> role=DIV level=2
+EVENT_OBJECT_HIDE on <div.a> role=DIV name="Heading" level=2
 EVENT_OBJECT_REORDER on <div> role=ROLE_SYSTEM_TOOLBAR IA2_STATE_HORIZONTAL
 EVENT_OBJECT_SHOW on <div.b> role=ROLE_SYSTEM_GROUPING name="Banner"
 IA2_EVENT_TEXT_INSERTED on <div> role=ROLE_SYSTEM_TOOLBAR IA2_STATE_HORIZONTAL new_text={'<obj>' start=0 end=1}

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

@@ -1178,14 +1178,28 @@ bool AXObject::ComputeAccessibilityIsIgnoredButIncludedInTree() const {
   if (!GetNode())
     return false;
 
+  // If the node is part of the user agent shadow dom, or has the explicit
+  // internal Role::kIgnored, they aren't interesting for paragraph navigation
+  // or LabelledBy/DescribedBy relationships.
+  if (RoleValue() == ax::mojom::Role::kIgnored ||
+      GetNode()->IsInUserAgentShadowRoot()) {
+    return false;
+  }
+
   // Always pass through Line Breaking objects, this is necessary to
   // detect paragraph edges, which are defined as hard-line breaks.
-  //
-  // Though if the node is part of the shadow dom, or has the explicit
-  // internal Role::kIgnored, they aren't interesting for paragraph
-  // navigation so exclude those cases.
-  return RoleValue() != ax::mojom::Role::kIgnored &&
-         !GetNode()->IsInUserAgentShadowRoot() && IsLineBreakingObject();
+  if (IsLineBreakingObject())
+    return true;
+
+  // Allow the browser side ax tree to access "visibility: hidden" nodes. This
+  // is useful for APIs that return the node referenced by aria-labeledby and
+  // aria-descibedby
+  if (GetLayoutObject() &&
+      GetLayoutObject()->Style()->Visibility() == EVisibility::kHidden) {
+    return true;
+  }
+
+  return false;
 }
 
 const AXObject* AXObject::DatetimeAncestor(int max_levels_to_check) const {
@@ -1491,8 +1505,15 @@ String AXObject::GetName(ax::mojom::NameFrom& name_from,
                          AXObject::AXObjectVector* name_objects) const {
   HeapHashSet<Member<const AXObject>> visited;
   AXRelatedObjectVector related_objects;
-  String text = TextAlternative(false, false, visited, name_from,
-                                &related_objects, nullptr);
+  // For purposes of computing a text alternative, if an ignored node is
+  // included in the tree, assume that it is the target of aria-labelledby or
+  // aria-describedby, since we can't tell yet whether that's the case. If it
+  // isn't exposed, the AT will never see the name anyways.
+  bool hidden_and_ignored_but_included_in_tree =
+      IsHiddenForTextAlternativeCalculation() &&
+      AccessibilityIsIgnoredButIncludedInTree();
+  String text = TextAlternative(false, hidden_and_ignored_but_included_in_tree,
+                                visited, name_from, &related_objects, nullptr);
 
   ax::mojom::Role role = RoleValue();
   if (!GetNode() ||
@@ -1513,8 +1534,16 @@ String AXObject::GetName(NameSources* name_sources) const {
   AXObjectSet visited;
   ax::mojom::NameFrom tmp_name_from;
   AXRelatedObjectVector tmp_related_objects;
-  String text = TextAlternative(false, false, visited, tmp_name_from,
-                                &tmp_related_objects, name_sources);
+  // For purposes of computing a text alternative, if an ignored node is
+  // included in the tree, assume that it is the target of aria-labelledby or
+  // aria-describedby, since we can't tell yet whether that's the case. If it
+  // isn't exposed, the AT will never see the name anyways.
+  bool hidden_and_ignored_but_included_in_tree =
+      IsHiddenForTextAlternativeCalculation() &&
+      AccessibilityIsIgnoredButIncludedInTree();
+  String text =
+      TextAlternative(false, hidden_and_ignored_but_included_in_tree, visited,
+                      tmp_name_from, &tmp_related_objects, name_sources);
   text = text.SimplifyWhiteSpace(IsHTMLSpace<UChar>);
   return text;
 }