Don't crash on OOM. b=353997 r+sr=darin

xpcom/ds/nsAtomTable.cpp

@@ -456,6 +456,7 @@ void* AtomImpl::operator new ( size_t size, const nsACString& aString ) CPP_THRO
      */
   size += aString.Length() * sizeof(char);
   AtomImpl* ii = NS_STATIC_CAST(AtomImpl*, ::operator new(size));
+  NS_ENSURE_TRUE(ii, nsnull);
 
   char* toBegin = &ii->mString[0];
   nsACString::const_iterator fromBegin, fromEnd;

xpcom/glue/nsArrayEnumerator.cpp

@@ -211,6 +211,7 @@ nsCOMArrayEnumerator::operator new (size_t size, const nsCOMArray_base& aArray)
     // do the actual allocation
     nsCOMArrayEnumerator * result =
         NS_STATIC_CAST(nsCOMArrayEnumerator*, ::operator new(size));
+    NS_ENSURE_TRUE(result, nsnull);
 
     // now need to copy over the values, and addref each one
     // now this might seem like a lot of work, but we're actually just