Node::getPseudoId has two overrides:

Node:
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/dom/Node.h?sq=package:chromium&dr=CSs&rcl=1471276009&l=258
virtual PseudoId getPseudoId() const { return PseudoIdNone; }

PseudoElement:
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/dom/PseudoElement.h?sq=package:chromium&dr=CSs&rcl=1471276009&l=46

PseudoId getPseudoId() const override { return m_pseudoId; }

This can be trivially devirtualized to something like (pseudo code):

(type == PseudoElement)? m_pseudoId : PseudoIdNone;

That will require a special optimization within WholeProgramDevirt pass in LLVM, and we should measure the list of types devirtualizable by this approach before actually implementing it.