Oilpan: Mark SVGElement::InvalidationGuard and SVGElement::InstanceUpdateBlocker STACK_ALLOCATED().
Oilpan: Mark SVGElement::InvalidationGuard and SVGElement::InstanceUpdateBlocker STACK_ALLOCATED().

and makes their element members Member<>.

BUG=357163

Review URL: https://codereview.chromium.org/334223009

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@176271 bbb929c8-8fbe-4397-9dbb-9b2b20218538

primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs