Fix invalidity in HitTestCache with LayoutParts.

Source/core/layout/LayoutPart.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Simon Hausmann <hausmann@kde.org>
  *           (C) 2000 Stefan Schimanski (1Stein@gmx.de)
  * Copyright (C) 2004, 2005, 2006, 2009 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 134 matching lines @@
 }
 
 bool LayoutPart::nodeAtPointOverWidget(HitTestResult& result, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction action)
 {
     bool hadResult = result.innerNode();
     bool inside = LayoutReplaced::nodeAtPoint(result, locationInContainer, accumulatedOffset, action);
 
     // Check to see if we are really over the widget itself (and not just in the border/padding area).
     if ((inside || result.isRectBasedTest()) && !hadResult && result.innerNode() == node())
         result.setIsOverWidget(contentBoxRect().contains(result.localPoint()));
+
+    // Do not cache hit tests as we don't get appropriate callbacks to invalidate the cache.
+    // This includes the border and padding areas for simplicity.
+    if (inside)

[esprehn, 2015/08/10 21:22:02]

Why not just use the isOverWidget check we did above? That avoids the
borders/padding and we're already doing it anyway.

+        result.setCacheable(false);
+
     return inside;
 }
 
 bool LayoutPart::nodeAtPoint(HitTestResult& result, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction action)
 {
     if (!widget() || !widget()->isFrameView() || !result.hitTestRequest().allowsChildFrameContent())
         return nodeAtPointOverWidget(result, locationInContainer, accumulatedOffset, action);
 
     FrameView* childFrameView = toFrameView(widget());
     LayoutView* childRoot = childFrameView->layoutView();
@@ skipping 171 matching lines @@
     if (widget() && widget()->isFrameView()) {
         FrameView* childFrameView = toFrameView(widget());
         PaintInvalidationState childViewPaintInvalidationState(*childFrameView->layoutView(), paintInvalidationState);
         toFrameView(widget())->invalidateTreeIfNeeded(childViewPaintInvalidationState);
     }
 
     LayoutReplaced::invalidatePaintOfSubtreesIfNeeded(paintInvalidationState);
 }
 
 }