Fixed bad calculations for determining total allocated size of a zone.

runtime/vm/zone_test.cc

Index: runtime/vm/zone_test.cc
diff --git a/runtime/vm/zone_test.cc b/runtime/vm/zone_test.cc
index c239320179c897f94f1bf1693ac3ea57bd17e2ab..38726ad0cc8aec955722878aed60dfdc2fb1b83f 100644
--- a/runtime/vm/zone_test.cc
+++ b/runtime/vm/zone_test.cc
@@ -201,7 +201,8 @@ UNIT_TEST_CASE(PrintZoneMemoryInfoToJSON) {
           OS::SCreate(string_stack_zone.GetZone(), "\"capacity\":%" Pd
                                                    ","
                                                    "\"used\":%" Pd "",
-                      zone.SizeInBytes(), zone.UsedSizeInBytes());
+                      zone.CapacityInBytes(), zone.SizeInBytes());
+      EXPECT_LE(zone.SizeInBytes(), zone.CapacityInBytes());
       EXPECT_SUBSTRING(size_buf, json);
     }
 
@@ -217,7 +218,8 @@ UNIT_TEST_CASE(PrintZoneMemoryInfoToJSON) {
           OS::SCreate(string_stack_zone.GetZone(), "\"capacity\":%" Pd
                                                    ","
                                                    "\"used\":%" Pd "",
-                      zone.SizeInBytes(), zone.UsedSizeInBytes());
+                      zone.CapacityInBytes(), zone.SizeInBytes());
+      EXPECT_LE(zone.SizeInBytes(), zone.CapacityInBytes());
       EXPECT_SUBSTRING(size_buf, json);
     }
   }