Add a flag to over approximate the weak closure during GC

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project 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 "src/v8.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
@@ skipping 2142 matching lines @@
   if (marking_deque_memory_committed_) {
     bool success = marking_deque_memory_->Uncommit(
         reinterpret_cast<Address>(marking_deque_memory_->address()),
         marking_deque_memory_->size());
     CHECK(success);
     marking_deque_memory_committed_ = false;
   }
 }
 
 
+void MarkCompactCollector::OverApproximateWeakClosure() {
+  GCTracer::Scope gc_scope(heap()->tracer(),
+                           GCTracer::Scope::MC_INCREMENTAL_WEAKCLOSURE);
+
+  RootMarkingVisitor root_visitor(heap());
+  isolate()->global_handles()->IterateObjectGroups(
+      &root_visitor, &IsUnmarkedHeapObjectWithHeap);
+  MarkImplicitRefGroups();
+
+  // Remove object groups after marking phase.
+  heap()->isolate()->global_handles()->RemoveObjectGroups();
+  heap()->isolate()->global_handles()->RemoveImplicitRefGroups();
+}
+
+
 void MarkCompactCollector::MarkLiveObjects() {
   GCTracer::Scope gc_scope(heap()->tracer(), GCTracer::Scope::MC_MARK);
   double start_time = 0.0;
   if (FLAG_print_cumulative_gc_stat) {
     start_time = base::OS::TimeCurrentMillis();
   }
   // The recursive GC marker detects when it is nearing stack overflow,
   // and switches to a different marking system.  JS interrupts interfere
   // with the C stack limit check.
   PostponeInterruptsScope postpone(isolate());
@@ skipping 2233 matching lines @@
   SlotsBuffer* buffer = *buffer_address;
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 }
 }  // namespace v8::internal