--- a/js/public/MemoryMetrics.h
+++ b/js/public/MemoryMetrics.h
@@ -32,17 +32,23 @@ struct TabSizes
 {
     enum Kind {
         Objects,
         Strings,
         Private,
         Other
     };
 
-    TabSizes() { mozilla::PodZero(this); }
+    TabSizes()
+      : objects(0)
+      , strings(0)
+      , private_(0)
+      , other(0)
+    {
+    }
 
     void add(Kind kind, size_t n) {
         switch (kind) {
             case Objects: objects  += n; break;
             case Strings: strings  += n; break;
             case Private: private_ += n; break;
             case Other:   other    += n; break;
             default:      MOZ_CRASH("bad TabSizes kind");