Rename childInsertionPoints to descendantInsertionPoints.

Ensure consistency with other function names.

BUG=None
Test=None; No behaviour change;

Review URL: https://codereview.chromium.org/59703004

git-svn-id: svn://svn.chromium.org/blink/trunk@161385 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[CSS Regions][CSS Shapes] Content in region doesn't respect shape-outside after initial layout pass

Although we set the size of a shape for shape-outside in RenderBlockFlow::insertFloatingObject based on the
float's size, the actual height of the float is not always resolved at that point. (Look at cases when the shape
has percentage based height or percentage based radius.) ShapeInfo::setShapeSize triggers a layout for 0 height
value, which will be overriden later, when RenderBlockFlow::positionNewFloats sets the actual size of the float (shape).
Thus it doesn't make sense to set the shape's size in insertFloatingObject and run those extra unnecessary layout passes,
since it'll be overriden anyways. I moved the shape size setting logic into RenderBlockFlow::positionNewFloats.

The problem showed up when we had a shape-outside ellipse with percentage based radius, and we inserted the content
with JavaScript into a region flow. The content has been layed out based on the 0 border radius, and relayout hasn't been
triggered when it flew into the flow. This change sets the shape size only when we already have the height of the float,
so the radius(es) can be resolved correctly, thus no unnecessary layout passes will happen and the layout will be correct as well.

Merged WebKit revision: http://trac.webkit.org/changeset/158630

Review URL: https://codereview.chromium.org/59873003

git-svn-id: svn://svn.chromium.org/blink/trunk@161386 bbb929c8-8fbe-4397-9dbb-9b2b20218538