Expand system font values during property parsing.

This is alancutter's patch, adjusted to work with the current master.

This patch removes special case handling of the font shorthand property.
Previously this property would be carried through to the style resolving
stage if system font values were used. This patch refactors this process
to happen in the CSS parser so that font is always expanded into longhand
values.

BUG=353932

Review URL: https://codereview.chromium.org/677103002

git-svn-id: svn://svn.chromium.org/blink/trunk@184449 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: make heap profiler work when there are nodes retained by weak references only

In some cases we get snapshots that contain nodes retained by weak references only (most likely due to a bug in v8, see crbug.com/426809), this breaks algorithm that caclculates dominators and leads to incorrect total heap snapshot size to be reported. This patch makes root dominator of such nodes. This way retained size of such orphan nodes is estimated correctly. The orphan node ids are still printed into console.

Shortcut references are considered the same way as weak refs from the dominance/retained size point of view.

BUG=426389

Review URL: https://codereview.chromium.org/679683002

git-svn-id: svn://svn.chromium.org/blink/trunk@184450 bbb929c8-8fbe-4397-9dbb-9b2b20218538