Add canvas line dash test

Add canvas line dash test
https://bugs.webkit.org/show_bug.cgi?id=150078
<rdar://problem/23082347>

Reviewed by Dean Jackson.

* Animometer/runner/resources/tests.js: Add line dash test.
* Animometer/tests/simple/resources/simple-canvas-paths.js:
(CanvasLineDashStage): Create a new stage with a default dash pattern and stroke style.
Maintain a step which will animate the dash.
(CanvasLineDashStage.prototype.animate): Render the line path with the dash. Increment
the dash offset to animate.
(CanvasPathBenchmark.prototype.createStage): Add the test.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@190921 268f45cc-cd09-0410-ab3c-d52691b4dbfc