Migrate from MathUtil::inverse() to gfx::Transform::GetInverse()

cc/layer_impl.cc

Index: cc/layer_impl.cc
diff --git a/cc/layer_impl.cc b/cc/layer_impl.cc
index 1f6e21ab0d8cac82a8968a47df25c73286acb364..cd6b24f22c5d8dce9bb2677ef9955d47775f5140 100644
--- a/cc/layer_impl.cc
+++ b/cc/layer_impl.cc
@@ -263,7 +263,13 @@ InputHandlerClient::ScrollStatus LayerImpl::tryScroll(const gfx::PointF& screenS
 
     if (!nonFastScrollableRegion().IsEmpty()) {
         bool clipped = false;
-        gfx::PointF hitTestPointInContentSpace = MathUtil::projectPoint(MathUtil::inverse(screenSpaceTransform()), screenSpacePoint, clipped);
+        // TODO: We shouldn't be applying a projection if screen space transform is uninvertible here.
+        //       Perhaps we should be returning ScrollOnMainThread if GetInverse returns false?
+        gfx::Transform inverseScreenSpaceTransform(gfx::Transform::kSkipInitialization);
+        if (!screenSpaceTransform().GetInverse(&inverseScreenSpaceTransform))
+            inverseScreenSpaceTransform.MakeIdentity();
+
+        gfx::PointF hitTestPointInContentSpace = MathUtil::projectPoint(inverseScreenSpaceTransform, screenSpacePoint, clipped);
         gfx::PointF hitTestPointInLayerSpace = gfx::ScalePoint(hitTestPointInContentSpace, 1 / contentsScaleX(), 1 / contentsScaleY());
         if (!clipped && nonFastScrollableRegion().Contains(gfx::ToRoundedPoint(hitTestPointInLayerSpace))) {
             TRACE_EVENT0("cc", "LayerImpl::tryScroll: Failed nonFastScrollableRegion");