Fix ClipMaskManager's SW-fallback logic (take 2)

https://codereview.chromium.org/1421533007/ (Fix ClipMaskManager's SW-fallback logic) had a logic error in it. It did not take into account createAlphaClipMask's fallback to non-Stenciled drawing (in drawElement).

This CL adds that logic and strips out the unnecessary changes (for clarity).

Review URL: https://codereview.chromium.org/1412883005
1 file changed