add some debugging to SkNVRefCnt

BUG=skia:

Review URL: https://codereview.chromium.org/745383003

bench/PicturePlaybackBench.cpp

@@ -210,10 +210,10 @@ public:
     }
 
 private:
-    BBH                      fBBH;
-    Mode                     fMode;
-    SkString                 fName;
-    SkAutoTDelete<SkPicture> fPic;
+    BBH                     fBBH;
+    Mode                    fMode;
+    SkString                fName;
+    SkAutoTUnref<SkPicture> fPic;
 };
 
 DEF_BENCH( return new TiledPlaybackBench(kNone,     kRandom); )

bench/RecordingBench.cpp

@@ -37,6 +37,6 @@ void RecordingBench::onDraw(const int loops, SkCanvas*) {
         SkPictureRecorder recorder;
         fSrc->playback(recorder.beginRecording(w, h, fUseBBH ? &factory : NULL,
                                                SkPictureRecorder::kComputeSaveLayerInfo_RecordFlag));
-        SkDELETE(recorder.endRecording());
+        SkSafeUnref(recorder.endRecording());
     }
 }

include/core/SkRefCnt.h

@@ -261,10 +261,23 @@ public:
 
     bool unique() const { return 1 == sk_acquire_load(&fRefCnt); }
     void    ref() const { sk_atomic_inc(&fRefCnt); }
-    void  unref() const { if (1 == sk_atomic_dec(&fRefCnt)) { SkDELETE((const Derived*)this); } }
+    void  unref() const {
+        int32_t prevValue = sk_atomic_dec(&fRefCnt);
+        SkASSERT(prevValue >= 1);
+        if (1 == prevValue) {
+            SkDELETE((const Derived*)this);
+        }
+    }
     void  deref() const { this->unref(); }  // Chrome prefers to call deref().
     int32_t getRefCnt() const { return fRefCnt; } // Used by Chrome unit tests.
 
+protected:
+#ifdef SK_DEBUG
+    ~SkNVRefCnt() {
+        SkASSERTF(0 == fRefCnt, "NVRefCnt was %d", fRefCnt);
+    }
+#endif
+
 private:
     mutable int32_t fRefCnt;
 };

tests/PictureBBHTest.cpp

@@ -109,13 +109,13 @@ static void test_clear(skiatest::Reporter* r, SkBBHFactory* factory) {
     // A picture that's just clear().
     src.beginRecording(1,1, factory)
         ->clear(SK_ColorGREEN);
-    SkAutoTDelete<SkPicture> srcPic(src.endRecording());
+    SkAutoTUnref<SkPicture> srcPic(src.endRecording());
 
     // A target canvas with an empty clip.
     SkCanvas* c = dst.beginRecording(1,1, NULL);
         c->clipRect(SkRect::MakeEmpty());
         srcPic->playback(c);
-    SkAutoTDelete<SkPicture> dstPic(dst.endRecording());
+    SkAutoTUnref<SkPicture> dstPic(dst.endRecording());
 
     // Should be Clip - Save - Clear - Restore.
     // Buggy implementations might return 1 (just Clip) or 3 (Clip - Save - Restore).

tests/PictureTest.cpp

@@ -1909,7 +1909,7 @@ DEF_TEST(Picture_BitmapLeak, r) {
     SkCanvas* canvas = rec.beginRecording(1920, 1200);
         canvas->drawBitmap(mut, 0, 0);
         canvas->drawBitmap(immut, 800, 600);
-    SkAutoTDelete<const SkPicture> pic(rec.endRecording());
+    SkAutoTUnref<const SkPicture> pic(rec.endRecording());
 
     // The picture shares the immutable pixels but copies the mutable ones.
     REPORTER_ASSERT(r, mut.pixelRef()->unique());

tests/RecordingXfermodeTest.cpp

@@ -115,7 +115,7 @@ class PictureStrategy : public RecordingStrategy {
                                                    SkIntToScalar(fHeight),
                                                    &factory);
         drawer.draw(canvas, canvasRect, mode);
-        SkAutoTDelete<SkPicture> picture(recorder.endRecording());
+        SkAutoTUnref<SkPicture> picture(recorder.endRecording());
 
         SkCanvas replayCanvas(fBitmap);
         replayCanvas.clear(0xffffffff);

tools/filtermain.cpp

@@ -661,7 +661,7 @@ struct OptTableEntry {
 
 
 static int filter_picture(const SkString& inFile, const SkString& outFile) {
-    SkAutoTDelete<SkPicture> inPicture;
+    SkAutoTUnref<SkPicture> inPicture;
 
     SkFILEStream inStream(inFile.c_str());
     if (inStream.isValid()) {