Rename RenderObject::setNeedsLayout to setNeedsLayoutAndFullRepaint

As we do full repaint on selfNeedsLayout, this renaming makes the
requirement explicit and into opting-in style. After this,
we can
- add opting-out-repaint version of setNeedsLayout;
- change setNeedsLayoutForcingRepaint calls to the new setNeedsLayout
  if repaint is not needed.

BUG=358460

Review URL: https://codereview.chromium.org/280633002

git-svn-id: svn://svn.chromium.org/blink/trunk@174329 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Navigation Transitions: added "NavigationTransitions" runtime flag.

This adds a flag to the runtime enabled flags to toggle navigation transitions.

Navigation Transitions: 

Design doc: https://docs.google.com/a/chromium.org/document/d/17jg1RRL3RI969cLwbKBIcoGDsPwqaEdBxafGNYGwiY4/edit# 
Implementation details: https://docs.google.com/a/chromium.org/document/d/1kREPtFJaeLoDKwrfmrYTD7DHCdxX1RzFBga2gNY8lyE/edit#heading=h.bng2kpmyvxq5 
BUG=370696

Review URL: https://codereview.chromium.org/287433003

git-svn-id: svn://svn.chromium.org/blink/trunk@174330 bbb929c8-8fbe-4397-9dbb-9b2b20218538