Make Document::visitedLinkState() return a reference

This CL makes the calling code look safer because it can never return null.

Review URL: https://codereview.chromium.org/35023006

git-svn-id: svn://svn.chromium.org/blink/trunk@160386 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add DEBUG-only plumbing and ASSERTS to check that freed RenderLayers don't pollute the layer lists.

This patch is a modified version of https://codereview.chromium.org/15888006/
for DEBUG-only computations to check the layer lists when freeing a RenderLayer,
to make sure that we don't end up with stale pointers.

BUG=

Review URL: https://codereview.chromium.org/35653003

git-svn-id: svn://svn.chromium.org/blink/trunk@160387 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[SVG] Devirtualize RenderSVGResource::resourceBoundingBox()

Only RenderSVGResourceFilter, RenderSVGResourceMasker and
RenderSVGResourceClipper have meaningful overrides, and all clients have
access to the qualified type.

R=pdr@chromium.org,schenney@chromium.org

Review URL: https://codereview.chromium.org/34463008

git-svn-id: svn://svn.chromium.org/blink/trunk@160388 bbb929c8-8fbe-4397-9dbb-9b2b20218538
CSS Animations: Add interpolation tests for webkit-transform

There are currently no test failures for web-animations-css. There are some expected failures with the legacy (non web-animations-css) implementation due to NOOP transforms being reported as "matrix(1, 0, 0, 1, 0, 0)" or similar instead of "none".

BUG=257591

Review URL: https://codereview.chromium.org/27455002

git-svn-id: svn://svn.chromium.org/blink/trunk@160389 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove dead code from Blink API

Also removed unnecessary duplicate method WebElement::document() (which
is also provided by WebNode).

R=abarth

Review URL: https://codereview.chromium.org/37523003

git-svn-id: svn://svn.chromium.org/blink/trunk@160390 bbb929c8-8fbe-4397-9dbb-9b2b20218538