HitTestLocation operates on flooredLayoutPoint which calls fromFloatFloor() to floor the LayoutUnit values. This produces different values when subpixel is on and may result in hitting different part of the document .
failed case: (hittesting on a transformed render layer's content)
Needs some debugging to see what the issues are.
the current behavior is correct as snapping any user generated input (even after a transform) would generate false results.
1. user clicks at position x,y
2. after applying the render transform, it gets the value of 11.6px float.
3. the pixelsnaped value is -> 12(*64)=768, while normal rounding value is -> round(11.6*64)=742.
4. This pixelsnapped value would make the hittest code find the layer painted at 768/64=12px, while the user clicked at 11.6px (after transform)