Simple BlinkGC heap compaction.

third_party/WebKit/Source/platform/heap/Visitor.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "platform/heap/Visitor.h"
 
 #include "platform/heap/BlinkGC.h"
 #include "platform/heap/MarkingVisitor.h"
 #include "platform/heap/ThreadState.h"
 #include "wtf/PtrUtil.h"
 #include <memory>
 
 namespace blink {
 
 std::unique_ptr<Visitor> Visitor::create(ThreadState* state,
                                          BlinkGC::GCType gcType) {
   switch (gcType) {
     case BlinkGC::GCWithSweep:
     case BlinkGC::GCWithoutSweep:
       return makeUnique<MarkingVisitor<Visitor::GlobalMarking>>(state);
+    case BlinkGC::GCWithSweepCompaction:
+      return makeUnique<MarkingVisitor<Visitor::GlobalMarkCompacting>>(state);
     case BlinkGC::TakeSnapshot:
       return makeUnique<MarkingVisitor<Visitor::SnapshotMarking>>(state);
     case BlinkGC::ThreadTerminationGC:
       return makeUnique<MarkingVisitor<Visitor::ThreadLocalMarking>>(state);
     case BlinkGC::ThreadLocalWeakProcessing:
       return makeUnique<MarkingVisitor<Visitor::WeakProcessing>>(state);
     default:
       ASSERT_NOT_REACHED();
   }
   return nullptr;
 }
 
 Visitor::Visitor(ThreadState* state, MarkingMode markingMode)
     : VisitorHelper(state), m_markingMode(markingMode) {
   // See ThreadState::runScheduledGC() why we need to already be in a
   // GCForbiddenScope before any safe point is entered.
-  state->enterGCForbiddenScope();
-
-  ASSERT(state->checkThread());
+  DCHECK(state->isGCForbidden());
+#if ENABLE(ASSERT)
+  DCHECK(state->checkThread());
+#endif
 }
 
-Visitor::~Visitor() {
-  state()->leaveGCForbiddenScope();
-}
+Visitor::~Visitor() {}
 
 }  // namespace blink