Revert "Simplify SVGSVGElement::getElementById method"

This reverts commit 54c88454a2f94147690450bc9b499361044c8ba3.

Reverting this fix because it assumed when SVG.getElementById is called the element is already part of the document and did not search svg subtree when the element is not found using above api.

Add test when svg element is not part of any document, it should still
be able to getElementById for it's child elements.

BUG=351831

Review URL: https://codereview.chromium.org/196193003

git-svn-id: svn://svn.chromium.org/blink/trunk@169157 bbb929c8-8fbe-4397-9dbb-9b2b20218538
remove unneeded isPrintingDevice

BUG=

Review URL: https://codereview.chromium.org/196603013

git-svn-id: svn://svn.chromium.org/blink/trunk@169158 bbb929c8-8fbe-4397-9dbb-9b2b20218538