Fix hover area for divs with css transforms

Source/core/rendering/RenderLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 2711 matching lines @@
     }
     return false;
 }
 
 // Compute the z-offset of the point in the transformState.
 // This is effectively projecting a ray normal to the plane of ancestor, finding where that
 // ray intersects target, and computing the z delta between those two points.
 static double computeZOffset(const HitTestingTransformState& transformState)
 {
     // We got an affine transform, so no z-offset
-    if (transformState.m_accumulatedTransform.isAffine())
-        return 0;
+    if (transformState.m_accumulatedTransform.isAffine()) {
+        // Non transformed layers are being hit last, not through or in-between transformed layers.
+        // The paint order says that the divs creating stacking contexts (including transforms) are painted after the
+        // other siblings so they should be hit tested in the reverse order. Also, a rotated div in a non-rotated parent
+        // should be hit in its entire area, not hit its parent's background, even if the z-coordinate is negative where
+        // the mouse is located.
+        return -std::numeric_limits<int>::max();
+    }
 
     // Flatten the point into the target plane
     FloatPoint targetPoint = transformState.mappedPoint();
 
     // Now map the point back through the transform, which computes Z.
     FloatPoint3D backmappedPoint = transformState.m_accumulatedTransform.mapPoint(FloatPoint3D(targetPoint));
     return backmappedPoint.z();
 }
 
 PassRefPtr<HitTestingTransformState> RenderLayer::createLocalTransformState(RenderLayer* rootLayer, RenderLayer* containerLayer,
@@ skipping 1431 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif