Provide more accurate results about used heap size via GetHeapStatistics.

src/spaces.h

Index: src/spaces.h
diff --git a/src/spaces.h b/src/spaces.h
index 69c52cc326a51d7e95c869bc922c4d4b018fbce9..60068c3d9110387f933a54ffcdc056e116e5e233 100644
--- a/src/spaces.h
+++ b/src/spaces.h
@@ -371,8 +371,13 @@ class Space : public Malloced {
   // Identity used in error reporting.
   AllocationSpace identity() { return id_; }
 
+  // Returns allocated size.
   virtual intptr_t Size() = 0;
 
+  // Returns size of objects. Can differ from the allocated size
+  // (e.g. see LargeObjectSpace).
+  virtual intptr_t SizeOfObjects() { return Size(); }
+
 #ifdef ENABLE_HEAP_PROTECTION
   // Protect/unprotect the space by marking it read-only/writable.
   virtual void Protect() = 0;
@@ -1715,6 +1720,8 @@ class OldSpaceFreeList BASE_EMBEDDED {
   // 'wasted_bytes'.  The size should be a non-zero multiple of the word size.
   MUST_USE_RESULT MaybeObject* Allocate(int size_in_bytes, int* wasted_bytes);
 
+  void MarkNodes();
+
  private:
   // The size range of blocks, in bytes. (Smaller allocations are allowed, but
   // will always result in waste.)
@@ -1813,6 +1820,8 @@ class FixedSizeFreeList BASE_EMBEDDED {
   // A failure is returned if no block is available.
   MUST_USE_RESULT MaybeObject* Allocate();
 
+  void MarkNodes();
+
  private:
   // Available bytes on the free list.
   intptr_t available_;
@@ -1884,6 +1893,8 @@ class OldSpace : public PagedSpace {
 
   virtual void PutRestOfCurrentPageOnFreeList(Page* current_page);
 
+  void MarkFreeListNodes() { free_list_.MarkNodes(); }
+
 #ifdef DEBUG
   // Reports statistics for the space
   void ReportStatistics();
@@ -1951,6 +1962,9 @@ class FixedSpace : public PagedSpace {
   virtual void DeallocateBlock(Address start,
                                int size_in_bytes,
                                bool add_to_freelist);
+
+  void MarkFreeListNodes() { free_list_.MarkNodes(); }
+
 #ifdef DEBUG
   // Reports statistic info of the space
   void ReportStatistics();
@@ -2191,6 +2205,10 @@ class LargeObjectSpace : public Space {
     return size_;
   }
 
+  virtual intptr_t SizeOfObjects() {
+    return objects_size_;
+  }
+
   int PageCount() {
     return page_count_;
   }
@@ -2242,7 +2260,7 @@ class LargeObjectSpace : public Space {
   LargeObjectChunk* first_chunk_;
   intptr_t size_;  // allocated bytes
   int page_count_;  // number of chunks
-
+  intptr_t objects_size_;  // size of objects
 
   // Shared implementation of AllocateRaw, AllocateRawCode and
   // AllocateRawFixedArray.