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

Source/core/page/TouchAdjustment.cpp

Index: Source/core/page/TouchAdjustment.cpp
diff --git a/Source/core/page/TouchAdjustment.cpp b/Source/core/page/TouchAdjustment.cpp
index ebf7ffd9e5db981a2c2e0900c43b1d9145ad9bf4..42e7956415fd268a7517790a53efc6b2bc417232 100644
--- a/Source/core/page/TouchAdjustment.cpp
+++ b/Source/core/page/TouchAdjustment.cpp
@@ -85,7 +85,10 @@ bool nodeRespondsToTapGesture(Node* node)
         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())