A11y: rely on AuraLinux AXPlatformNodeDelegate for getting parent index.

AXPlatformNodeAuraLinux was returning always 0 for GetIndexInParent, and
adding an ATK specific implementation of get_index_in_parent. As a result,
AX API would not return the right value, even if ATK would.

This fix makes get_index_in_parent rely on GetIndexInParent, and
GetIndexInParent use the delegate to obtain the value.

Bug: None.
Change-Id: Ic8d79da9f481c2cf92f28eefeb6b2030cce5e657
Reviewed-on: https://chromium-review.googlesource.com/806037
Commit-Queue: José Dapena Paz <jose.dapena@lge.com>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521720}

ui/accessibility/platform/ax_platform_node_auralinux.cc

@@ -104,20 +104,9 @@ static gint ax_platform_node_auralinux_get_index_in_parent(
   ui::AXPlatformNodeAuraLinux* obj =
     AtkObjectToAXPlatformNodeAuraLinux(atk_object);
 
-  if (!obj || !obj->GetParent())
+  if (!obj)
     return -1;
 
-  AtkObject* obj_parent = obj->GetParent();
-
-  unsigned child_count = atk_object_get_n_accessible_children(obj_parent);
-  for (unsigned index = 0; index < child_count; index++) {
-    AtkObject* child = atk_object_ref_accessible_child(obj_parent, index);
-    bool atk_object_found = child == atk_object;
-    g_object_unref(child);
-    if (atk_object_found)
-      return index;
-  }
-
   return obj->GetIndexInParent();
 }
 
@@ -1086,7 +1075,10 @@ void AXPlatformNodeAuraLinux::NotifyAccessibilityEvent(ui::AXEvent event_type) {
 }
 
 int AXPlatformNodeAuraLinux::GetIndexInParent() {
-  return 0;
+  if (!GetParent())
+    return -1;
+
+  return delegate_->GetIndexInParent();
 }
 
 void AXPlatformNodeAuraLinux::SetExtentsRelativeToAtkCoordinateType(

ui/accessibility/platform/test_ax_node_wrapper.cc

@@ -167,7 +167,7 @@ AXPlatformNode* TestAXNodeWrapper::GetFromNodeID(int32_t id) {
 }
 
 int TestAXNodeWrapper::GetIndexInParent() const {
-  return -1;
+  return node_ ? node_->index_in_parent() : -1;
 }
 
 gfx::AcceleratedWidget