[heap] Add basic infrastructure for Minor Mark-Compact collector

src/flag-definitions.h

Index: src/flag-definitions.h
diff --git a/src/flag-definitions.h b/src/flag-definitions.h
index d1d641e4dac1f5edc8eaa76e3f28bebd5fd07387..ac192a2365d0706fbc1ec3c0ad6bf693c30c7487 100644
--- a/src/flag-definitions.h
+++ b/src/flag-definitions.h
@@ -727,6 +727,8 @@ DEFINE_INT(min_progress_during_incremental_marking_finalization, 32,
            "least this many unmarked objects")
 DEFINE_INT(max_incremental_marking_finalization_rounds, 3,
            "at most try this many times to finalize incremental marking")
+DEFINE_BOOL(minor_mc, false, "perform young generation mark compact GCs")
+DEFINE_NEG_IMPLICATION(minor_mc, incremental_marking)
 DEFINE_BOOL(black_allocation, false, "use black allocation")
 DEFINE_BOOL(concurrent_sweeping, true, "use concurrent sweeping")
 DEFINE_BOOL(parallel_compaction, true, "use parallel compaction")