When you transform a textfield, e.g., rotate it 10 degrees, you see horrible repaint problems.
(1) The caret doesn't blink properly.
(2) You see two focus rings, one offset from the other
(3) The contents don't always update right
*** Bug 20772 has been marked as a duplicate of this bug. ***
Bug 20772 has a testcase.
Split off focus ring drawing into bug 21906.
Split off caret drawing into bug 21907.
Content updating is broken by LayoutState issues. When typing in a textarea, FrameView::layout() is laying out a subtree, in which case it pushes a LayoutState for the root (which is ignoring transforms). RenderBox::computeAbsoluteRepaintRect() then picks up that LayoutState and gets an offset that ignores transforms.
*** Bug 86626 has been marked as a duplicate of this bug. ***
See also bug 94985.
Caret issue was fixed by bug 15671.