Bug 1359049 - Improve gray marking assertions to cover object private GC pointers r=sfink

js/src/gc/Verifier.cpp

@@ -657,7 +657,8 @@ CheckGrayMarkingTracer::checkCell(Cell* cell)
         tenuredCell->isMarked(GRAY))
     {
         failures++;
-        fprintf(stderr, "Found black to gray edge %p\n", cell);
+        fprintf(stderr, "Found black to gray edge to %s %p\n",
+                GCTraceKindToAscii(cell->getTraceKind()), cell);
         dumpCellPath();
     }
 }

js/src/vm/NativeObject.h

@@ -1225,6 +1225,8 @@ class NativeObject : public ShapedObject
     }
 
     void setPrivateGCThing(gc::Cell* cell) {
+        MOZ_ASSERT_IF(IsMarkedBlack(this),
+                      !JS::GCThingIsMarkedGray(JS::GCCellPtr(cell, cell->getTraceKind())));
         void** pprivate = &privateRef(numFixedSlots());
         privateWriteBarrierPre(pprivate);
         *pprivate = reinterpret_cast<void*>(cell);