Bug 1878356: Trim non-breaking spaces from acc name prefixes, suffixes, r=Jamie

This revision modifies LocalAccessible::Name such that the function trims
non-breaking spaces from the beginning and end of accessible names. We already
compress all ASCII whitespace and trim it from the prefixes and suffixes of
accessible names - this change just extends that trimming to non-breaking spaces
for the exterior ends of the name string only. This revision implements a new
function, TrimNonBreakingSpaces, which does the trimming. Finally, this revision
removes five expected failures from the web platform tests.

Differential Revision: https://phabricator.services.mozilla.com/D203993

accessible/base/nsCoreUtils.cpp

@@ -546,6 +546,32 @@ bool nsCoreUtils::IsWhitespaceString(const nsAString& aString) {
   return iterBegin == iterEnd;
 }
 
+void nsCoreUtils::TrimNonBreakingSpaces(nsAString& aString) {
+  if (aString.IsEmpty()) {
+    return;
+  }
+
+  // Find the index past the last nbsp prefix character.
+  constexpr char16_t nbsp{0xA0};
+  size_t startIndex = 0;
+  while (aString.CharAt(startIndex) == nbsp) {
+    startIndex++;
+  }
+
+  // Find the index before the first nbsp suffix character.
+  size_t endIndex = aString.Length() - 1;
+  while (endIndex > startIndex && aString.CharAt(endIndex) == nbsp) {
+    endIndex--;
+  }
+  if (startIndex > endIndex) {
+    aString.Truncate();
+    return;
+  }
+
+  // Trim the string down, removing the non-breaking space characters.
+  aString = Substring(aString, startIndex, endIndex - startIndex + 1);
+}
+
 bool nsCoreUtils::AccEventObserversExist() {
   nsCOMPtr<nsIObserverService> obsService = services::GetObserverService();
   NS_ENSURE_TRUE(obsService, false);

accessible/base/nsCoreUtils.h

@@ -305,6 +305,11 @@ class nsCoreUtils {
            aChar == 0xa0;
   }
 
+  /**
+   * Remove non-breaking spaces from the beginning and end of the string.
+   */
+  static void TrimNonBreakingSpaces(nsAString& aString);
+
   /*
    * Return true if there are any observers of accessible events.
    */

accessible/generic/LocalAccessible.cpp

@@ -127,6 +127,7 @@ ENameValueFlag LocalAccessible::Name(nsString& aName) const {
   if (!aName.IsEmpty()) return eNameOK;
 
   ENameValueFlag nameFlag = NativeName(aName);
+  nsCoreUtils::TrimNonBreakingSpaces(aName);
   if (!aName.IsEmpty()) return nameFlag;
 
   // In the end get the name from tooltip.

testing/web-platform/meta/accname/name/comp_text_node.html.ini

@@ -1,15 +0,0 @@
-[comp_text_node.html]
-  [span[role=button\] with text node, with leading/trailing non-breaking space]
-    expected: FAIL
-
-  [div[role=heading\] with text node, with leading/trailing non-breaking space]
-    expected: FAIL
-
-  [button with text node, with leading/trailing non-breaking space]
-    expected: FAIL
-
-  [heading with text node, with leading/trailing non-breaking space]
-    expected: FAIL
-
-  [link with text node, with leading/trailing non-breaking space]
-    expected: FAIL