Polish EmbedderHeapTracer and move some checks from blink to v8

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index e1eaba0b92cf0a92bb6ceff2bd10a5dd6decdda8..c0a3f0d0229a1c1dfb17c0fd34b78c58e3ba4085 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -2148,7 +2148,7 @@ void MarkCompactCollector::TracePossibleWrapper(JSObject* js_object) {
       js_object->GetInternalField(0) &&
       js_object->GetInternalField(0) != heap_->undefined_value() &&
       js_object->GetInternalField(1) != heap_->undefined_value()) {
-    DCHECK(reinterpret_cast<intptr_t>(js_object->GetInternalField(0)) % 2 == 1);
+    DCHECK(reinterpret_cast<intptr_t>(js_object->GetInternalField(0)) % 2 == 0);
     wrappers_to_trace().push_back(std::pair<void*, void*>(
         reinterpret_cast<void*>(js_object->GetInternalField(0)),
         reinterpret_cast<void*>(js_object->GetInternalField(1))));