Touch adjustment: don't treat iframes as clickable by default

Source/core/page/TouchAdjustment.cpp

 /*
  * Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies)
  *
  * 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
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 67 matching lines @@
 typedef void (*AppendSubtargetsForNode)(Node*, SubtargetGeometryList&);
 typedef float (*DistanceFunction)(const IntPoint&, const IntRect&, const SubtargetGeometry&);
 
 // Takes non-const Node* because isContentEditable is a non-const function.
 bool nodeRespondsToTapGesture(Node* node)
 {
     if (node->willRespondToMouseClickEvents() || node->willRespondToMouseMoveEvents())
         return true;
     if (node->isElementNode()) {
         Element* element = toElement(node);
-        if (element->isMouseFocusable())
+        // Tapping on a text field or other focusable item should trigger adjustment, except
+        // that iframe elements are hard-coded to support focus but the effect is often invisible
+        // so they should be excluded.
+        if (element->isMouseFocusable() && !isHTMLIFrameElement(element))
             return true;
         // Accept nodes that has a CSS effect when touched.
         if (element->childrenOrSiblingsAffectedByActive() || element->childrenOrSiblingsAffectedByHover())
             return true;
     }
     if (RenderStyle* renderStyle = node->renderStyle()) {
         if (renderStyle->affectedByActive() || renderStyle->affectedByHover())
             return true;
     }
     return false;
@@ skipping 405 matching lines @@
 
 bool findBestZoomableArea(Node*& targetNode, IntRect& targetArea, const IntPoint& touchHotspot, const IntRect& touchArea, const WillBeHeapVector<RefPtrWillBeMember<Node> >& nodes)
 {
     IntPoint targetPoint;
     TouchAdjustment::SubtargetGeometryList subtargets;
     TouchAdjustment::compileZoomableSubtargets(nodes, subtargets);
     return TouchAdjustment::findNodeWithLowestDistanceMetric(targetNode, targetPoint, targetArea, touchHotspot, touchArea, subtargets, TouchAdjustment::zoomableIntersectionQuotient);
 }
 
 } // namespace blink