https://bugs.webkit.org/show_bug.cgi?id=112592

Reviewed by Dirk Schulze.

Source/WebCore:

First pass at computing the padded or inset boundary of a polygon.  This version does not handle
self-intersecting polygons, or values of shape-padding large enough to change the shape of the
original polygon. The implementation computes an offset edge for each polgon edge, where the offset
edge is parallel to the original edge and separated by shape-padding. The padded polygon's vertices
are the intersections of each pair of adjacent offset edges. When adjacent offset edges do not intersect,
because they share a reflex vertex in the original polygon, an approximation to a circular arc
connects the offset edges.

Tests: fast/exclusions/shape-inside/shape-inside-polygon-padding-001.html
       fast/exclusions/shape-inside/shape-inside-polygon-padding-002.html
       fast/exclusions/shape-inside/shape-inside-polygon-padding-003.html

* rendering/ExclusionPolygon.cpp:
(WebCore::isReflexVertex): Just moved this function earlier in the file.
(WebCore::inwardEdgeNormal): Unit vector that's perpindicular to the edge and that points inwards.
(WebCore::outwardEdgeNormal): Unit vector that's perpindicular to the edge and that points outwards.
(WebCore::appendArc): Append a linear approximation to a circular arc to a vector of vertices.
(WebCore::computeShapePaddingBounds): Return a polygon whose edges are all inset by shape-padding from m_polygon.
(WebCore::computeShapeMarginBounds): Just a stub, see bug 112917.
(WebCore::ExclusionPolygon::shapePaddingBounds): Lazily use computeShapePaddingBounds() to initialize m_paddingBounds.
(WebCore::ExclusionPolygon::shapeMarginBounds): Lazily use computeShapeMarginBounds() to initialize m_marginBounds.
(WebCore::ExclusionPolygon::getIncludedIntervals): Now based on the value of shapePaddingBounds().
(WebCore::ExclusionPolygon::firstIncludedIntervalLogicalTop): Now based on the value of shapePaddingBounds().
* rendering/ExclusionPolygon.h:
(WebCore::ExclusionPolygon::ExclusionPolygon):

LayoutTests:

Verify that the CSS shape-padding property works correctly for some simple polygonal shapes:
a rectangle, a rectangle rotated 45 degress, and rectangular shape with a single reflex vertex.

* fast/exclusions/shape-inside/shape-inside-polygon-padding-001-expected.html: Added.
* fast/exclusions/shape-inside/shape-inside-polygon-padding-001.html: Added.
* fast/exclusions/shape-inside/shape-inside-polygon-padding-002-expected.html: Added.
* fast/exclusions/shape-inside/shape-inside-polygon-padding-002.html: Added.
* fast/exclusions/shape-inside/shape-inside-polygon-padding-003-expected.html: Added.
* fast/exclusions/shape-inside/shape-inside-polygon-padding-003.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@147111 268f45cc-cd09-0410-ab3c-d52691b4dbfc