Remove ancestor walk for non-SVG RenderObjects in willBeRemovedFromTree()

This patch removes the recursive setNeedsBoundariesUpdate() calls
that were done in RenderObject::willBeRemovedFromTree().

This patch has three main components:
1) The virtual RenderObject::needsBoundariesUpdate() has been removed
as it was never called.
2) The virtual RenderObject::isSVG() has been added for determining
whether a RenderObject is an SVG renderer. All SVG renderers have
been updated to return true for isSVG(). See the following diagram
for more information:
https://docs.google.com/a/chromium.org/drawings/d/1nayJX5XcclYj_-blbVuakVNjVWdRAzC5i5s6xBeHfzA/edit
3) RenderObject::willBeRemovedFromTree() now only calls
setNeedsBoundariesUpdate() if the parent renderer is SVG.

Review URL: https://codereview.chromium.org/108203005

git-svn-id: svn://svn.chromium.org/blink/trunk@164056 bbb929c8-8fbe-4397-9dbb-9b2b20218538