guard against NaN in path is rect

Recent rewrite of SkPath::isRect() did not check against
sequences with NaN and infinity.

R=kjlubick@google.com

Bug: oss-fuzz:7882
Change-Id: I9315f68e4c53c37fda819adc6d57d6b3e3acc1c6
Reviewed-on: https://skia-review.googlesource.com/122783
Commit-Queue: Cary Clark <caryclark@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Auto-Submit: Cary Clark <caryclark@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>

src/core/SkPath.cpp

@@ -480,6 +480,9 @@ bool SkPath::isRectContour(bool allowPartial, int* currVerb, const SkPoint** pts
                 if (lineDelta.fX && lineDelta.fY) {
                     return false; // diagonal
                 }
+                if (!lineDelta.isFinite()) {
+                    return false; // path contains infinity or NaN
+                }
                 if (lineStart == lineEnd) {
                     break; // single point on side OK
                 }