Fix PagedSpace size accounting.

src/spaces.h

Index: src/spaces.h
diff --git a/src/spaces.h b/src/spaces.h
index efed18ec6d4778c26ef7bd1fd1067e68230b43ff..2e6c0b938c5fdf0f96f5e955d5c0d3f26645bbe2 100644
--- a/src/spaces.h
+++ b/src/spaces.h
@@ -1457,9 +1457,8 @@ class AllocationStats BASE_EMBEDDED {
 
   // Waste free bytes (available -> waste).
   void WasteBytes(int size_in_bytes) {
-    size_ -= size_in_bytes;
+    ASSERT(size_in_bytes >= 0);
     waste_ += size_in_bytes;
-    ASSERT(size_ >= 0);
   }
 
  private:
@@ -1857,7 +1856,8 @@ class PagedSpace : public Space {
   // no attempt to add area to free list is made.
   int Free(Address start, int size_in_bytes) {
     int wasted = free_list_.Free(start, size_in_bytes);
-    accounting_stats_.DeallocateBytes(size_in_bytes - wasted);
+    accounting_stats_.DeallocateBytes(size_in_bytes);
+    accounting_stats_.WasteBytes(wasted);
     return size_in_bytes - wasted;
   }