Address MSVS 2013 warning C4146: unary minus operator applied to unsigned type, result still unsign…

runtime/vm/object_set.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_OBJECT_SET_H_
 #define VM_OBJECT_SET_H_
 
 #include "platform/utils.h"
 #include "vm/globals.h"
 #include "vm/raw_object.h"
@@ skipping 13 matching lines @@
   ~ObjectSet() {
     delete[] allocation_;
   }
 
   void Init(uword start, uword end) {
     start_ = start;
     end_ = end;
     ASSERT(start_ <= end_);
     size_ = SizeFor((end_ - start_) >> kWordSizeLog2);
     allocation_ = new uword[size_];
-    data_ = &allocation_[-((start >> kWordSizeLog2) / kBitsPerWord)];
-    ASSERT(allocation_ == &data_[(start >> kWordSizeLog2) / kBitsPerWord]);
+    const intptr_t skipped_bitfield_words =
+        (start >> kWordSizeLog2) / kBitsPerWord;
+    data_ = &allocation_[-skipped_bitfield_words];
+    ASSERT(allocation_ == &data_[skipped_bitfield_words]);
     Clear();
   }
 
   bool Contains(RawObject* raw_obj) const {
     uword raw_addr = RawObject::ToAddr(raw_obj);
     ASSERT(raw_addr >= start_);
     ASSERT(raw_addr < end_);
     uword i = raw_addr >> kWordSizeLog2;
     uword mask = (static_cast<uword>(1) << (i % kBitsPerWord));
     return (data_[i / kBitsPerWord] & mask) != 0;
@@ skipping 59 matching lines @@
   // The inclusive maximum address in this ObjectMap.
   // Used by FastClear
   uword max_;
 
   DISALLOW_COPY_AND_ASSIGN(ObjectSet);
 };
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_SET_H_