Oilpan: Implement a GC to take a heap snapshot

Source/platform/heap/Heap.h

Index: Source/platform/heap/Heap.h
diff --git a/Source/platform/heap/Heap.h b/Source/platform/heap/Heap.h
index 550b6a174f557551da25d6142ae73b51c4528061..491c08dbb5bf91bae93d06f45b1180f92b3d1db4 100644
--- a/Source/platform/heap/Heap.h
+++ b/Source/platform/heap/Heap.h
@@ -386,6 +386,7 @@ public:
     virtual void removeFromHeap() = 0;
     virtual void sweep() = 0;
     virtual void makeConsistentForGC() = 0;
+    virtual void makeConsistentForMutator() = 0;
 
 #if defined(ADDRESS_SANITIZER)
     virtual void poisonObjects(ObjectsToPoison, Poisoning) = 0;
@@ -474,6 +475,7 @@ public:
     virtual void removeFromHeap() override;
     virtual void sweep() override;
     virtual void makeConsistentForGC() override;
+    virtual void makeConsistentForMutator() override;
 #if defined(ADDRESS_SANITIZER)
     virtual void poisonObjects(ObjectsToPoison, Poisoning) override;
 #endif
@@ -536,6 +538,7 @@ public:
     virtual void removeFromHeap() override;
     virtual void sweep() override;
     virtual void makeConsistentForGC() override;
+    virtual void makeConsistentForMutator() override;
 #if defined(ADDRESS_SANITIZER)
     virtual void poisonObjects(ObjectsToPoison, Poisoning) override;
 #endif
@@ -694,6 +697,7 @@ public:
 
     virtual void clearFreeLists() { }
     void makeConsistentForGC();
+    void makeConsistentForMutator();
 #if ENABLE(ASSERT)
     virtual bool isConsistentForGC() = 0;
 #endif