Bug 1455511: Always prune the accessibility tree for sliders. r=surkov

It doesn't make sense for a slider to have descendants and this confuses NVDA.

MozReview-Commit-ID: 2A3gqTSu38g

--HG--
extra : rebase_source : 8776da7b23601eb3f1ec9e9711f9f9cd9eedd849

accessible/base/nsAccUtils.cpp

@@ -436,10 +436,15 @@ nsAccUtils::MustPrune(Accessible* aAccessible)
 {
   roles::Role role = aAccessible->Role();
 
+  return
+    // Always prune the tree for sliders, as it doesn't make sense for a slider
+    // to have descendants and this confuses NVDA.
+    role == roles::SLIDER ||
     // Don't prune the tree for certain roles if the tree is more complex than
     // a single text leaf.
-  return
+    (
-    (role == roles::MENUITEM ||
+     (
+      role == roles::MENUITEM ||
       role == roles::COMBOBOX_OPTION ||
       role == roles::OPTION ||
       role == roles::ENTRY ||
@@ -448,9 +453,10 @@ nsAccUtils::MustPrune(Accessible* aAccessible)
       role == roles::PUSHBUTTON ||
       role == roles::TOGGLE_BUTTON ||
       role == roles::GRAPHIC ||
-     role == roles::SLIDER ||
       role == roles::PROGRESSBAR ||
-     role == roles::SEPARATOR) &&
+      role == roles::SEPARATOR
+     ) &&
      aAccessible->ContentChildCount() == 1 &&
-    aAccessible->ContentChildAt(0)->IsTextLeaf();
+     aAccessible->ContentChildAt(0)->IsTextLeaf()
+    );
 }