Update css3/filters/should-not-have-compositing-layer for FCM.

This test checks if the layer is promoted by checking if compositing
is enabled, which does not work when ForceCompositingMode is turned on.

Instead, have the test dump its composited layer tree, and the results
will show if the filtered image was promoted to a composited layer or
not.

R=enne@chromium.org, senorblanco@chromium.org
BUG=361729

Review URL: https://codereview.chromium.org/228553004

git-svn-id: svn://svn.chromium.org/blink/trunk@171228 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make compositing/video/video-poster.html test dump the layer tree.

Instead of testing if the video was promoted to a composited layer by
checking if compositing mode is enabled (this is not a valid check
under ForceCompositingMode), dump the composited layer tree so that
the promotion or not is explicitly visible.

R=enne@chromium.org
BUG=361729

Review URL: https://codereview.chromium.org/228783006

git-svn-id: svn://svn.chromium.org/blink/trunk@171230 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[SVG Fonts] Fix <font-face> element leak document

Reported by hajimehoshi@: A svg document with <font-face> was never destructed from a reference cycle.

This patch breaks the reference cycle by making the reference from SVGFontFaceSource to SVGFontFaceElement weak.
SVGFontFaceSource only exist for in-document font face reference, so this change is safe.

This patch also validates SVGFontData's weak-ref to SVGFontFaceElement. SVGFontData should be only used while the document is alive. This CL changes the weak-ref to WeakPtr and ensure the svg tree is alive before reference.

TEST=LayoutTests/svg/svg-font-face-leak-document.html
BUG=270000

Review URL: https://codereview.chromium.org/216563002

git-svn-id: svn://svn.chromium.org/blink/trunk@171231 bbb929c8-8fbe-4397-9dbb-9b2b20218538
nextTraversingShadowTree should walk up from a shadow host to its shadow root when the shadow host has no next element.

When walking up from a given node to a shadow host which hosts the shadow root of the given node,
the shadow host is the last element of a tree, ElementTraversal::next will return 0.
However, if the shadow host is still in some shadow tree, we need to walk up from the shadow host
to its shadow root.

BUG=359854
TEST=fast/dom/SelectorAPI/only-shadow-host-in-shadow-tree.html

Review URL: https://codereview.chromium.org/225023036

git-svn-id: svn://svn.chromium.org/blink/trunk@171232 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Unreviewed rebaseline for XP/virtual-directwrite

TBR=dglazkov@chromium.org
BUG=

Review URL: https://codereview.chromium.org/232483002

git-svn-id: svn://svn.chromium.org/blink/trunk@171233 bbb929c8-8fbe-4397-9dbb-9b2b20218538