Allow degenerate matrices in SourceToDestinationProjection

Matrices can be non-invertible on the web, such as scale(0).

Bug:809701

Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: Ia5b1b893f0a0d922b8b40d45577f8be0bff16ca2
Reviewed-on: https://chromium-review.googlesource.com/981688
Commit-Queue: Tien-Ren Chen <trchen@chromium.org>
Reviewed-by: Tien-Ren Chen <trchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546220}

third_party/WebKit/Source/platform/graphics/paint/GeometryMapper.cpp

@@ -16,7 +16,6 @@ const TransformationMatrix& GeometryMapper::SourceToDestinationProjection(
   bool success = false;
   const auto& result =
       SourceToDestinationProjectionInternal(source, destination, success);
-  DCHECK(success);
   return result;
 }