[heap] Synchronize young generation GC with concurrent marking.

src/heap/heap.h

 // 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.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <vector>
 
@@ skipping 572 matching lines @@
     kStrongRootListLength = kStringTableRootIndex,
     kSmiRootsStart = kStringTableRootIndex + 1
   };
 
   enum FindMementoMode { kForRuntime, kForGC };
 
   enum HeapState { NOT_IN_GC, SCAVENGE, MARK_COMPACT, MINOR_MARK_COMPACT };
 
   enum UpdateAllocationSiteMode { kGlobal, kCached };
 
-  // Taking this lock prevents the GC from entering a phase that relocates
+  // Taking this mutex prevents the GC from entering a phase that relocates
   // object references.
-  class RelocationLock {
-   public:
-    explicit RelocationLock(Heap* heap) : heap_(heap) {
-      heap_->relocation_mutex_.Lock();
-    }
-
-    ~RelocationLock() { heap_->relocation_mutex_.Unlock(); }
-
-   private:
-    Heap* heap_;
-  };
+  base::Mutex* relocation_mutex() { return &relocation_mutex_; }
 
   // Support for partial snapshots.  After calling this we have a linear
   // space to write objects in each space.
   struct Chunk {
     uint32_t size;
     Address start;
     Address end;
   };
   typedef std::vector<Chunk> Reservation;
 
@@ skipping 2039 matching lines @@
   friend class PagedSpace;
   DISALLOW_COPY_AND_ASSIGN(AllocationObserver);
 };
 
 V8_EXPORT_PRIVATE const char* AllocationSpaceName(AllocationSpace space);
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_