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

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index f4ef6953fd6352bc59b9d64726c93ec6379a7a97..91e7ce943ca0a7c02f928bda7cd882964f439a02 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -684,6 +684,14 @@ class Heap {
 #endif
   }
 
+  static inline bool IsYoungGenerationCollector(GarbageCollector collector) {
+    return collector == SCAVENGER || collector == MINOR_MARK_COMPACTOR;
+  }
+
+  static inline GarbageCollector YoungGenerationCollector() {
+    return (FLAG_minor_mc) ? MINOR_MARK_COMPACTOR : SCAVENGER;
+  }
+
   V8_EXPORT_PRIVATE static double HeapGrowingFactor(double gc_speed,
                                                     double mutator_speed);
 
@@ -1773,6 +1781,8 @@ class Heap {
 
   // Performs a major collection in the whole heap.
   void MarkCompact();
+  // Performs a minor collection of just the young generation.
+  void MinorMarkCompact();
 
   // Code to be run before and after mark-compact.
   void MarkCompactPrologue();