Get rid of deprecated methods accessing mutator_thread_ instead of current thread

runtime/vm/snapshot.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_SNAPSHOT_H_
 #define VM_SNAPSHOT_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/bitfield.h"
@@ skipping 698 matching lines @@
   }
 
   void WriteDouble(double value) {
     stream_.WriteBytes(reinterpret_cast<const uint8_t*>(&value), sizeof(value));
   }
 
  protected:
   BaseWriter(uint8_t** buffer,
              ReAlloc alloc,
              intptr_t initial_size)
-      : StackResource(Isolate::Current()),
+      : StackResource(Thread::Current()),
         stream_(buffer, alloc, initial_size) {
     ASSERT(buffer != NULL);
     ASSERT(alloc != NULL);
   }
   ~BaseWriter() { }
 
   void ReserveHeader() {
     // Make room for recording snapshot buffer size.
     stream_.set_current(stream_.buffer() + Snapshot::kHeaderSize);
   }
@@ skipping 391 matching lines @@
  private:
   SnapshotWriter* writer_;
   bool as_references_;
 
   DISALLOW_COPY_AND_ASSIGN(SnapshotWriterVisitor);
 };
 
 }  // namespace dart
 
 #endif  // VM_SNAPSHOT_H_