Migrate LongJumpScope to Thread.

runtime/vm/longjump.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_LONGJUMP_H_
 #define VM_LONGJUMP_H_
 
 #include <setjmp.h>
 
 #include "vm/allocation.h"
 #include "vm/isolate.h"
 
 namespace dart {
 
 class Error;
 
 class LongJumpScope : public StackResource {
  public:
   LongJumpScope()
-    : StackResource(Isolate::Current()),
+    : StackResource(Thread::Current()),
       top_(NULL),
-      base_(Isolate::Current()->long_jump_base()) {
-    Isolate::Current()->set_long_jump_base(this);
+      base_(Thread::Current()->long_jump_base()) {
+    Thread::Current()->set_long_jump_base(this);
   }
 
   ~LongJumpScope() {
-    Isolate::Current()->set_long_jump_base(base_);
+    Thread::Current()->set_long_jump_base(base_);
   }
 
   jmp_buf* Set();
   void Jump(int value, const Error& error);
 
   // Would it be safe to use this longjump?
   //
   // Checks to make sure that the jump would not cross Dart frames.
   bool IsSafeToJump();
 
  private:
   jmp_buf environment_;
   StackResource* top_;
   LongJumpScope* base_;
 
   DISALLOW_COPY_AND_ASSIGN(LongJumpScope);
 };
 
 }  // namespace dart
 
 #endif  // VM_LONGJUMP_H_