Keep zone cached in SnapshotReader to allow removing ZoneHandle(Isolate*) interface.

runtime/vm/native_entry.h

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_NATIVE_ENTRY_H_
 #define VM_NATIVE_ENTRY_H_
 
 #include "platform/memory_sanitizer.h"
 
 #include "vm/allocation.h"
@@ skipping 56 matching lines @@
   static RawObject* DN_Helper##name(Isolate* isolate,                          \
                                     Thread* thread,                            \
                                     Zone* zone,                                \
                                     NativeArguments* arguments)
 
 
 // Natives should throw an exception if an illegal argument or null is passed.
 // type name = value.
 #define GET_NON_NULL_NATIVE_ARGUMENT(type, name, value)                        \
   const Instance& __##name##_instance__ =                                      \
-      Instance::CheckedHandle(isolate, value);                                 \
+      Instance::CheckedHandle(zone, value);                                    \
   if (!__##name##_instance__.Is##type()) {                                     \
     const Array& __args__ = Array::Handle(Array::New(1));                      \
     __args__.SetAt(0, __##name##_instance__);                                  \
     Exceptions::ThrowByType(Exceptions::kArgument, __args__);                  \
   }                                                                            \
   const type& name = type::Cast(__##name##_instance__);
 
 
 // Natives should throw an exception if an illegal argument is passed.
 // type name = value.
 #define GET_NATIVE_ARGUMENT(type, name, value)                                 \
   const Instance& __##name##_instance__ =                                      \
-      Instance::CheckedHandle(isolate, value);                                 \
+      Instance::CheckedHandle(zone, value);                                    \
   type& name = type::Handle(isolate);                                          \
   if (!__##name##_instance__.IsNull()) {                                       \
     if (!__##name##_instance__.Is##type()) {                                   \
       const Array& __args__ = Array::Handle(Array::New(1));                    \
       __args__.SetAt(0, __##name##_instance__);                                \
       Exceptions::ThrowByType(Exceptions::kArgument, __args__);                \
     }                                                                          \
   }                                                                            \
   name ^= value;
 
@@ skipping 12 matching lines @@
                                                uword pc);
   static const uint8_t* ResolveSymbol(uword pc);
   static void NativeCallWrapper(Dart_NativeArguments args,
                                 Dart_NativeFunction func);
   static const ExternalLabel& NativeCallWrapperLabel();
 };
 
 }  // namespace dart
 
 #endif  // VM_NATIVE_ENTRY_H_