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

runtime/vm/service_test.cc

 // Copyright (c) 2013, 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 "vm/dart_api_impl.h"
 #include "vm/dart_entry.h"
 #include "vm/debugger.h"
@@ skipping 59 matching lines @@
   growable ^= result.At(5);
   // Append dummy isolate id to parameter values.
   growable.Add(dummy_isolate_id);
   array = Array::MakeArray(growable);
   result.SetAt(5, array);
   return result.raw();
 }
 
 
 static RawArray* EvalF(Dart_Handle lib, const char* fmt, ...) {
-  Isolate* isolate = Isolate::Current();
-
   va_list args;
   va_start(args, fmt);
   intptr_t len = OS::VSNPrint(NULL, 0, fmt, args);
   va_end(args);
 
-  char* buffer = isolate->current_zone()->Alloc<char>(len + 1);
+  char* buffer = Thread::Current()->zone()->Alloc<char>(len + 1);
   va_list args2;
   va_start(args2, fmt);
   OS::VSNPrint(buffer, (len + 1), fmt, args2);
   va_end(args2);
 
   return Eval(lib, buffer);
 }
 
 
 static RawFunction* GetFunction(const Class& cls, const char* name) {
@@ skipping 530 matching lines @@
       Eval(lib, "[0, port, '0', '_getCpuProfile', ['tags'], ['Bogus']]");
   Service::HandleIsolateMessage(isolate, service_msg);
   handler.HandleNextMessage();
   // Expect error.
   EXPECT_SUBSTRING("\"error\"", handler.msg());
 }
 
 #endif  // !defined(TARGET_ARCH_ARM64)
 
 }  // namespace dart