Bug 937227 - zero-initialize fields in nsWindowSizes; r=njn

dom/base/nsWindowMemoryReporter.h

@@ -47,6 +47,8 @@ public:
       #define ZERO_SIZE(kind, mSize)  mSize(0),
       FOR_EACH_SIZE(ZERO_SIZE)
       #undef ZERO_SIZE
+      mDOMEventTargetsCount(0),
+      mDOMEventListenersCount(0),
       mArenaStats(),
       mMallocSizeOf(aMallocSizeOf)
   {}