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

runtime/vm/flow_graph_compiler.h

 // 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.
 
 #ifndef VM_FLOW_GRAPH_COMPILER_H_
 #define VM_FLOW_GRAPH_COMPILER_H_
 
 #include "vm/allocation.h"
 #include "vm/assembler.h"
 #include "vm/code_descriptors.h"
@@ skipping 159 matching lines @@
 
   Label* entry_label() { return &entry_label_; }
 
   // Implementation is in architecture specific file.
   virtual void GenerateCode(FlowGraphCompiler* compiler, intptr_t stub_ix);
 
   const char* Name() const {
     const char* kFormat = "Deopt stub for id %d, reason: %s";
     const intptr_t len = OS::SNPrint(NULL, 0, kFormat,
         deopt_id(), DeoptReasonToCString(reason())) + 1;
-    char* chars = Isolate::Current()->current_zone()->Alloc<char>(len);
+    char* chars = Thread::Current()->zone()->Alloc<char>(len);
     OS::SNPrint(chars, len, kFormat,
         deopt_id(), DeoptReasonToCString(reason()));
     return chars;
   }
 
  private:
   Label entry_label_;
 
   DISALLOW_COPY_AND_ASSIGN(CompilerDeoptInfoWithStub);
 };
@@ skipping 526 matching lines @@
   Array& inlined_code_intervals_;
   const GrowableArray<const Function*>& inline_id_to_function_;
   const GrowableArray<intptr_t>& caller_inline_id_;
 
   DISALLOW_COPY_AND_ASSIGN(FlowGraphCompiler);
 };
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_COMPILER_H_