Check pointers convertible not values in sk_sp.

include/core/SkRefCnt.h

Index: include/core/SkRefCnt.h
diff --git a/include/core/SkRefCnt.h b/include/core/SkRefCnt.h
index 9e8f3be61c33456de32384af7a25f84326d30989..de3d98b3c4d98f3891211df0ebdc7c6a2c21c3ea 100644
--- a/include/core/SkRefCnt.h
+++ b/include/core/SkRefCnt.h
@@ -249,8 +249,7 @@ public:
      *  created sk_sp both have a reference to it.
      */
     sk_sp(const sk_sp<T>& that) : fPtr(SkSafeRef(that.get())) {}
-    template <typename U,
-              typename = skstd::enable_if_t<skstd::is_convertible<U, T>::value>>
+    template <typename U, typename = skstd::enable_if_t<skstd::is_convertible<U*, T*>::value>>
     sk_sp(const sk_sp<U>& that) : fPtr(SkSafeRef(that.get())) {}
 
     /**
@@ -259,8 +258,7 @@ public:
      *  No call to ref() or unref() will be made.
      */
     sk_sp(sk_sp<T>&& that) : fPtr(that.release()) {}
-    template <typename U,
-              typename = skstd::enable_if_t<skstd::is_convertible<U, T>::value>>
+    template <typename U, typename = skstd::enable_if_t<skstd::is_convertible<U*, T*>::value>>
     sk_sp(sk_sp<U>&& that) : fPtr(that.release()) {}
 
     /**
@@ -287,8 +285,7 @@ public:
         this->reset(SkSafeRef(that.get()));
         return *this;
     }
-    template <typename U,
-              typename = skstd::enable_if_t<skstd::is_convertible<U, T>::value>>
+    template <typename U, typename = skstd::enable_if_t<skstd::is_convertible<U*, T*>::value>>
     sk_sp<T>& operator=(const sk_sp<U>& that) {
         this->reset(SkSafeRef(that.get()));
         return *this;
@@ -303,8 +300,7 @@ public:
         this->reset(that.release());
         return *this;
     }
-    template <typename U,
-              typename = skstd::enable_if_t<skstd::is_convertible<U, T>::value>>
+    template <typename U, typename = skstd::enable_if_t<skstd::is_convertible<U*, T*>::value>>
     sk_sp<T>& operator=(sk_sp<U>&& that) {
         this->reset(that.release());
         return *this;
@@ -356,7 +352,7 @@ public:
     }
 
 private:
-    T*  fPtr;
+    T* fPtr;
 };
 
 template <typename T, typename... Args>