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

runtime/vm/disassembler_x64.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 "vm/disassembler.h"
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_IA32.
 #if defined(TARGET_ARCH_X64)
 #include "platform/utils.h"
 #include "vm/allocation.h"
@@ skipping 780 matching lines @@
       obj.IsFunction() ||
       obj.IsICData() ||
       obj.IsField()) {
     return obj.ToCString();
   }
 
   const Class& clazz = Class::Handle(obj.clazz());
   const char* full_class_name = clazz.ToCString();
   const char* format = "instance of %s";
   intptr_t len = OS::SNPrint(NULL, 0, format, full_class_name) + 1;
-  char* chars = Isolate::Current()->current_zone()->Alloc<char>(len);
+  char* chars = Thread::Current()->zone()->Alloc<char>(len);
   OS::SNPrint(chars, len, format, full_class_name);
   return chars;
 }
 
 
 void DisassemblerX64::AppendAddressToBuffer(uint8_t* addr_byte_ptr) {
   uword addr = reinterpret_cast<uword>(addr_byte_ptr);
   AppendToBuffer("%#" Px "", addr);
   // Try to print as heap object or stub name
   if (((addr & kSmiTagMask) == kHeapObjectTag) &&
@@ skipping 1140 matching lines @@
   }
   hex_buffer[hex_index] = '\0';
   if (out_instr_len) {
     *out_instr_len = instruction_length;
   }
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64