Fix behavior of sk_sp::reset(T*) and add unittest.

Previously, sk_sp::reset(T* t) did not release its own reference
if its internal pointer was the same as 't'. This leaks a reference.
Now always release the current reference when non-nullptr.

Review URL: https://codereview.chromium.org/1767983002

1 files changed, 2 insertions, 4 deletions

diff --git a/include/core/SkRefCnt.h b/include/core/SkRefCnt.h
index 9b05ad4969..d33117751e 100644
--- a/include/core/SkRefCnt.h
+++ b/include/core/SkRefCnt.h
@@ -338,10 +338,8 @@ public:
      *  No call to ref() will be made.
      */
     void reset(T* ptr = nullptr) {
-        if (fPtr != ptr) {
-            SkSafeUnref(fPtr);
-            fPtr = ptr;
-        }
+        SkSafeUnref(fPtr);
+        fPtr = ptr;
     }
 
     /**