[heap] Temporarily disable compaction for concurrent marking.

src/flag-definitions.h

Index: src/flag-definitions.h
diff --git a/src/flag-definitions.h b/src/flag-definitions.h
index 07446ed1e46669bbc4e53129aa5ad8153a7c9061..73b1033688a538a44a5e02958bf6f1f2b1779ba1 100644
--- a/src/flag-definitions.h
+++ b/src/flag-definitions.h
@@ -725,6 +725,9 @@ DEFINE_INT(v8_os_page_size, 0, "override OS page size (in KBytes)")
 DEFINE_BOOL(always_compact, false, "Perform compaction on every full GC")
 DEFINE_BOOL(never_compact, false,
             "Never perform compaction on full GC - testing only")
+// TODO(ulan): enable compaction for concurrent marking when it correctly
+// records slots to evacuation candidates.
+DEFINE_IMPLICATION(concurrent_marking, never_compact)
 DEFINE_BOOL(compact_code_space, true, "Compact code space on full collections")
 DEFINE_BOOL(cleanup_code_caches_at_gc, true,
             "Flush code caches in maps during mark compact cycle.")