Have Document::timeline() / Document::transitionTimeline() return a reference

Have Document::timeline() / Document::transitionTimeline() return a reference
instead of a pointer as they can never return null. This makes the calling code
look safer and gets rid of a few unnecessary null checks.

R=adamk

Review URL: https://codereview.chromium.org/176903004

git-svn-id: svn://svn.chromium.org/blink/trunk@167940 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fix ASSERT failure in RenderGeomtryMap for SVGs

SVGRenderSupport::mapLocalToContainer() was trying to apply transforms
in the incorrect order. Specifically, it would attempt to apply its
localToParentTransform before its localToBorderBoxTransform. This
was causing an ASSERT to fail when the computed transforms didn't
match up to those computed by RenderGeometryMap.

BUG=302719

Review URL: https://codereview.chromium.org/143363004

git-svn-id: svn://svn.chromium.org/blink/trunk@167941 bbb929c8-8fbe-4397-9dbb-9b2b20218538