Let viewport-percentage lengths relative to the layout size

When the page is scaled up, the logical viewport will be bigger than
the visible viewport . According to the spec, viewport-percentage
lengths should be relative to the size of the "initial containing block"
which is the logical viewport not the visible viewport.

Removed Document::viewportSize() and RenderView::viewportSize() because
of no more usages.

BUG=289707
TEST=css3/viewport-percentage-lengths/viewport-percentage-lenths-scaled.html and existing css3/viewport-percentage-lengths for the unchanged non-scaled behavior.

Review URL: https://chromiumcodereview.appspot.com/23449029

git-svn-id: svn://svn.chromium.org/blink/trunk@157934 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[Font Load Events] Implement new font load events

* Make loadingdone's event object have a list of fonts successfully loaded
* Add loadingerror event, which is fired with a list of fonts failed to load
* Drop the per-font events (loadstart, load, error)

spec: http://dev.w3.org/csswg/css-font-load-events/#FontFaceSet-events

BUG=53213
TEST=fast/css

Review URL: https://chromiumcodereview.appspot.com/24196003

git-svn-id: svn://svn.chromium.org/blink/trunk@157935 bbb929c8-8fbe-4397-9dbb-9b2b20218538