Bug 1800048: Don't expose the LINKS_TO relation via ATK and IA2. r=morgan

This relation isn't part of the ATK and IA2 specs.
In ATK and the older way of retrieving relations in IA2, we have to calculate all relations.
Since LINKS_TO can be slow and it isn't supported by ATK and IA2 anyway, let's just not expose it at all for them.

Differential Revision: https://phabricator.services.mozilla.com/D161775

accessible/base/RelationTypeMap.h

@@ -86,5 +86,5 @@ RELATIONTYPE(ERRORMSG, "error", ATK_RELATION_ERROR_MESSAGE, NAVRELATION_ERROR,
 RELATIONTYPE(ERRORMSG_FOR, "error for", ATK_RELATION_ERROR_FOR,
              NAVRELATION_ERROR_FOR, IA2_RELATION_ERROR_FOR)
 
-RELATIONTYPE(LINKS_TO, "links to", ATK_RELATION_LINKS_TO, NAVRELATION_LINKS_TO,
-             IA2_RELATION_LINKS_TO)
+RELATIONTYPE(LINKS_TO, "links to", ATK_RELATION_NULL, NAVRELATION_LINKS_TO,
+             IA2_RELATION_NULL)

accessible/tests/browser/e10s/browser_caching_relations.js

@@ -215,7 +215,12 @@ addAccessibleTask(
 
     await testCachedRelation(link, RELATION_LINKS_TO, item2);
   },
-  { chrome: true, iframe: true, remoteIframe: true }
+  {
+    chrome: true,
+    // IA2 doesn't have a LINKS_TO relation and Windows non-cached
+    // RemoteAccessible uses IA2, so we can't run these tests in this case.
+    topLevel: !isWinNoCache, iframe: !isWinNoCache, remoteIframe: !isWinNoCache
+  }
 );
 
 /*

other-licenses/atk-1.0/atk/atkrelationtype.h

@@ -80,7 +80,6 @@ G_BEGIN_DECLS
  *@ATK_RELATION_ERROR_FOR: Reciprocal of %ATK_RELATION_ERROR_MESSAGE. Indicates that this object
  * contains an error message describing an invalid condition in the target object(s). @Since:
  * ATK_2.26.
- *@ATK_RELATION_LINKS_TO: For an anchor link, indicates the element that the link is anchored to.
  *@ATK_RELATION_LAST_DEFINED: Not used, this value indicates the end of the enumeration.
  * 
  *Describes the type of the relation
@@ -108,7 +107,6 @@ typedef enum
   ATK_RELATION_DETAILS_FOR,
   ATK_RELATION_ERROR_MESSAGE,
   ATK_RELATION_ERROR_FOR,
-  ATK_RELATION_LINKS_TO,
   ATK_RELATION_LAST_DEFINED
 } AtkRelationType;
 

other-licenses/ia2/AccessibleRelation.idl

@@ -172,9 +172,6 @@ const WCHAR *const IA2_RELATION_ERROR = L"error";
 /** This object is the error message for the target object. */
 const WCHAR *const IA2_RELATION_ERROR_FOR = L"errorFor";
 
-/** The target object is the anchor referenced by this link. */
-const WCHAR *const IA2_RELATION_LINKS_TO = L"linksTo";
-
 ///@}
 
 /** This interface gives access to an object's set of relations.