Implement NSAccessibilityScrollToVisibleAction on Mac

third_party/WebKit/Source/modules/accessibility/AXObject.cpp

 /*
  * Copyright (C) 2008, 2009, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
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@@ skipping 1498 matching lines @@
         && objectMax - currentScrollOffset <= viewportMax)
         return currentScrollOffset;
 
     // Center the object in the viewport.
     return (objectMin + objectMax - viewportMin - viewportMax) / 2;
 }
 
 void AXObject::scrollToMakeVisibleWithSubFocus(const IntRect& subfocus) const
 {
     // Search up the parent chain until we find the first one that's scrollable.
-    AXObject* scrollParent = parentObject();
+    const AXObject* scrollParent = this;

[Elly Fong-Jones, 2016/09/26 16:25:39]

what's up with this?

[dmazzoni, 2016/09/26 18:00:40]

It's part of the change.

Previously we didn't have a use case for calling
scrollToMakeVisibleWithSubFocus when the object itself
is the one that needs to scroll. Previously we'd call
it on an object like a heading or a button and it'd
search up for the nearest scrollable container.

In this case we want to call it on the document, which
is scrollable - but we want to tell it to scroll to a
certain bounding box rect (subfocus).

     ScrollableArea* scrollableArea = 0;
     while (scrollParent) {
         scrollableArea = scrollParent->getScrollableAreaIfScrollable();
         if (scrollableArea)
             break;
         scrollParent = scrollParent->parentObject();
     }
     if (!scrollParent || !scrollableArea)
         return;
 
@@ skipping 266 matching lines @@
 
 DEFINE_TRACE(AXObject)
 {
     visitor->trace(m_children);
     visitor->trace(m_parent);
     visitor->trace(m_cachedLiveRegionRoot);
     visitor->trace(m_axObjectCache);
 }
 
 } // namespace blink