As is all too often the case, no one ever activated this feature on Windows. I only noticed it because a number of tests fail due to missing functionality.
Created attachment 228413 [details] Patch
Enabling this feature corrects the following tests: fast/canvas/canvas-clip-path.html fast/canvas/canvas-fill-path.html fast/canvas/canvas-path-addPath.html fast/canvas/canvas-path-isPointInPath.html fast/canvas/canvas-path-isPointInStroke.html fast/canvas/canvas-stroke-path.html
Committed r166660: <http://trac.webkit.org/changeset/166660>