Migrate most uses of Isolate::current_zone to Thread::zone.

runtime/vm/snapshot_test.cc

 // Copyright (c) 2012, 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.
 
 #include "platform/globals.h"
 
 #include "include/dart_tools_api.h"
 #include "platform/assert.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart_api_impl.h"
@@ skipping 43 matching lines @@
 
 
 static uint8_t* malloc_allocator(
     uint8_t* ptr, intptr_t old_size, intptr_t new_size) {
   return reinterpret_cast<uint8_t*>(realloc(ptr, new_size));
 }
 
 
 static uint8_t* zone_allocator(
     uint8_t* ptr, intptr_t old_size, intptr_t new_size) {
-  Zone* zone = Isolate::Current()->current_zone();
+  Zone* zone = Thread::Current()->zone();
   return zone->Realloc<uint8_t>(ptr, old_size, new_size);
 }
 
 
 // Compare two Dart_CObject object graphs rooted in first and
 // second. The second graph will be destroyed by this operation no matter
 // whether the graphs are equal or not.
 static void CompareDartCObjects(Dart_CObject* first, Dart_CObject* second) {
   // Return immediately if entering a cycle.
   if (second->type == Dart_CObject_kNumberOfTypes) return;
@@ skipping 2832 matching lines @@
   StackZone zone(Isolate::Current());
   uint8_t* buffer;
   MessageWriter writer(&buffer, &zone_allocator, true);
   writer.WriteInlinedObjectHeader(kOmittedObjectId);
   // For performance, we'd like single-byte headers when ids are omitted.
   // If this starts failing, consider renumbering the snapshot ids.
   EXPECT_EQ(1, writer.BytesWritten());
 }
 
 }  // namespace dart