Expose a lower bound of malloc'd memory via heap statistics

src/zone.h

Index: src/zone.h
diff --git a/src/zone.h b/src/zone.h
index 753e2035d3ac612060cb1391c33f29db5df9110f..4973405a4ec1b7bf07d7080feac62423419a7794 100644
--- a/src/zone.h
+++ b/src/zone.h
@@ -7,7 +7,7 @@
 
 #include <limits>
 
-#include "src/allocation.h"
+#include "src/base/accounting_allocator.h"
 #include "src/base/logging.h"
 #include "src/globals.h"
 #include "src/hashmap.h"
@@ -33,9 +33,9 @@ class Segment;
 //
 // Note: The implementation is inherently not thread safe. Do not use
 // from multi-threaded code.
-class Zone final {
+class Zone {
  public:
-  Zone();
+  explicit Zone(base::AccountingAllocator* allocator);
   ~Zone();
 
   // Allocate 'size' bytes of memory in the Zone; expands the Zone by
@@ -64,6 +64,8 @@ class Zone final {
 
   size_t allocation_size() const { return allocation_size_; }
 
+  base::AccountingAllocator* allocator() const { return allocator_; }
+
  private:
   // All pointers returned from New() have this alignment.  In addition, if the
   // object being allocated has a size that is divisible by 8 then its alignment
@@ -114,6 +116,8 @@ class Zone final {
   Address position_;
   Address limit_;
 
+  base::AccountingAllocator* allocator_;
+
   Segment* segment_head_;
 };
 
@@ -165,6 +169,16 @@ class ZoneAllocationPolicy final {
   Zone* zone_;
 };
 
+class ZoneForTesting : public Zone {
+ public:
+  ZoneForTesting() : Zone(&allocator_) {}
+  ~ZoneForTesting() = default;
+
+ private:
+  base::AccountingAllocator allocator_;
+
+  DISALLOW_COPY_AND_ASSIGN(ZoneForTesting);
+};
 
 // ZoneLists are growable lists with constant-time access to the
 // elements. The list itself and all its elements are allocated in the