Initialize "weakness_type" field in global handles

BUG=4122
R=vogelheim@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/1143143002

Cr-Commit-Position: refs/heads/master@{#28504}

src/global-handles.cc

@@ -76,6 +76,7 @@ class GlobalHandles::Node {
     index_ = static_cast<uint8_t>(index);
     DCHECK(static_cast<int>(index_) == index);
     set_state(FREE);
+    set_weakness_type(NORMAL_WEAK);
     set_in_new_space_list(false);
     parameter_or_next_free_.next_free = *first_free;
     *first_free = this;