Verify that heap object iterator stays within page bound.

BUG=

Review URL: https://codereview.chromium.org/823583010

Cr-Commit-Position: refs/heads/master@{#25999}

src/heap/spaces-inl.h

@@ -91,6 +91,12 @@ HeapObject* HeapObjectIterator::FromCurrentPage() {
     int obj_size = (size_func_ == NULL) ? obj->Size() : size_func_(obj);
     cur_addr_ += obj_size;
     DCHECK(cur_addr_ <= cur_end_);
+    // TODO(hpayer): Remove the debugging code.
+    if (cur_addr_ > cur_end_) {
+      space_->heap()->isolate()->PushStackTraceAndDie(0xaaaaaaaa, obj, NULL,
+                                                      obj_size);
+    }
+
     if (!obj->IsFiller()) {
       DCHECK_OBJECT_SIZE(obj_size);
       return obj;