[CSS Regions][CSS Shapes] Update updateShapeAndSegmentsForCurrentLineInFlowThread to deal better with the first lines
[CSS Regions][CSS Shapes] Update updateShapeAndSegmentsForCurrentLineInFlowThread to deal better with the first lines

We have a complex condition in updateShapeAndSegmentsForCurrentLineInFlowThread, which is
adjusting the first line to the shape's top. This patch adds two boolean to make that clear.

Merged WebKit revision: http://trac.webkit.org/changeset/158015

Review URL: https://codereview.chromium.org/50263005

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@160874 bbb929c8-8fbe-4397-9dbb-9b2b20218538

primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs