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

test/unittests/wasm/module-decoder-unittest.cc

Index: test/unittests/wasm/module-decoder-unittest.cc
diff --git a/test/unittests/wasm/module-decoder-unittest.cc b/test/unittests/wasm/module-decoder-unittest.cc
index 136b9f26acd800cec35335bb57accce9d8edc83a..44e78653e3922dbd3fc4d9629330839ce315ca0f 100644
--- a/test/unittests/wasm/module-decoder-unittest.cc
+++ b/test/unittests/wasm/module-decoder-unittest.cc
@@ -779,7 +779,8 @@ class WasmSignatureDecodeTest : public TestWithZone {};
 
 TEST_F(WasmSignatureDecodeTest, Ok_v_v) {
   static const byte data[] = {0, 0};
-  Zone zone;
+  base::AccountingAllocator allocator;
+  Zone zone(&allocator);
   FunctionSig* sig =
       DecodeWasmSignatureForTesting(&zone, data, data + arraysize(data));