IDL cleanup: remove blank lines in extended attribute lists

Another minor cleanup (simplifies grepping and improves style).

TBR=haraken

Review URL: https://codereview.chromium.org/67763003

git-svn-id: svn://svn.chromium.org/blink/trunk@162276 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[CSSRegions] Model regions functionality using anonymous regions

Allow any non-replaced block to behave like a region. When an element is styled with the -webkit-flow-from
property, instead of making the renderer a RenderRegion, we let the original renderer be created the same
way and we add a region block as an anonymous child for the renderer.
The anonymous child, instance of new RenderNamedFlowFragment class, will be responsible for the fragmentation
of the named flow thread content.

A RenderBlockFlow will keep a reference to a RenderNamedFlowFragment (RenderRegion) inside its rare data
structures.

In the long term, RenderFlowThread and RenderRegion will implement basic fragmentation functionality.
The specialization classes RenderNamedFlowThread, based on RenderFlowThread, and RenderNamedFlowFragment,
based on RenderRegion, will implement the CSSRegions functionality.

BUG=317834

Review URL: https://codereview.chromium.org/68343013

git-svn-id: svn://svn.chromium.org/blink/trunk@162277 bbb929c8-8fbe-4397-9dbb-9b2b20218538