Oilpan: Implement a GC to take a heap snapshot

Source/platform/heap/MarkingVisitorImpl.h

Index: Source/platform/heap/MarkingVisitorImpl.h
diff --git a/Source/platform/heap/MarkingVisitorImpl.h b/Source/platform/heap/MarkingVisitorImpl.h
index 27c8964e1f03c987231b0d8aa3313476146b6479..3265caa2dacdc26c2eca8e02514691e19e8e94a6 100644
--- a/Source/platform/heap/MarkingVisitorImpl.h
+++ b/Source/platform/heap/MarkingVisitorImpl.h
@@ -70,6 +70,9 @@ protected:
     inline void registerWeakMembers(const void* closure, const void* objectPointer, WeakCallback callback)
     {
         ASSERT(toDerived()->markingMode() != Visitor::WeakProcessing);
+        // We don't want to run weak processings when taking a snapshot.
+        if (toDerived()->markingMode() == Visitor::SnapshotMarking)
+            return;
         Heap::pushThreadLocalWeakCallback(const_cast<void*>(closure), const_cast<void*>(objectPointer), callback);
     }
 
@@ -117,6 +120,9 @@ protected:
     inline void registerWeakCellWithCallback(void** cell, WeakCallback callback)
     {
         ASSERT(toDerived()->markingMode() != Visitor::WeakProcessing);
+        // We don't want to run weak processings when taking a snapshot.
+        if (toDerived()->markingMode() == Visitor::SnapshotMarking)
+            return;
         Heap::pushGlobalWeakCallback(cell, callback);
     }