fuzz hang fix and pathops client debugging

The ASAN fuzzer on chrome caught a hanging state.

To capture the data, allow the pathops client debugging
to run in a release build.

TBR=reed@google.com
BUG=665295

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4834

Change-Id: I6b2c2baabd63994f63aa730d2ee7828986b5ab89
Reviewed-on: https://skia-review.googlesource.com/4834
Commit-Queue: Cary Clark <caryclark@google.com>
Reviewed-by: Cary Clark <caryclark@google.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/pathops/SkOpSegment.cpp b/src/pathops/SkOpSegment.cpp
index f3f874710e..a1818d36cd 100644
--- a/src/pathops/SkOpSegment.cpp
+++ b/src/pathops/SkOpSegment.cpp
@@ -837,12 +837,19 @@ SkOpSpanBase* SkOpSegment::markAndChaseDone(SkOpSpanBase* start, SkOpSpanBase* e
     markDone(minSpan);
     SkOpSpanBase* last = nullptr;
     SkOpSegment* other = this;
+    SkOpSpan* priorDone = nullptr;
+    SkOpSpan* lastDone = nullptr;
     while ((other = other->nextChase(&start, &step, &minSpan, &last))) {
         if (other->done()) {
             SkASSERT(!last);
             break;
         }
+        if (lastDone == minSpan || priorDone == minSpan) {
+            return nullptr;
+        }
         other->markDone(minSpan);
+        priorDone = lastDone;
+        lastDone = minSpan;
     }
     return last;
 }