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

runtime/vm/bitmap.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/bitmap.h"
 
 #include "platform/assert.h"
 #include "vm/object.h"
 
 namespace dart {
@@ skipping 36 matching lines @@
     // Bits not covered by the backing store are implicitly false.
     if (!value) return;
     // Grow the backing store if necessary.
     intptr_t byte_offset = bit_offset >> kBitsPerByteLog2;
     if (byte_offset >= data_size_in_bytes_) {
       uint8_t* old_data = data_;
       intptr_t old_size = data_size_in_bytes_;
       data_size_in_bytes_ =
           Utils::RoundUp(byte_offset + 1, kIncrementSizeInBytes);
       ASSERT(data_size_in_bytes_ > 0);
-      data_ = Isolate::Current()->current_zone()->Alloc<uint8_t>(
+      data_ = Thread::Current()->zone()->Alloc<uint8_t>(
           data_size_in_bytes_);
       ASSERT(data_ != NULL);
       memmove(data_, old_data, old_size);
       memset(&data_[old_size], 0, (data_size_in_bytes_ - old_size));
     }
   }
   SetBit(bit_offset, value);
 }
 
 
@@ skipping 39 matching lines @@
   uint8_t mask = 1U << bit_remainder;
   ASSERT(data_ != NULL);
   if (value) {
     data_[byte_offset] |= mask;
   } else {
     data_[byte_offset] &= ~mask;
   }
 }
 
 }  // namespace dart