Revert "[vm] Revise Dart_IntegerToHexCString to avoid dependency on Bigint"

runtime/vm/object.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/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/become.h"
@@ skipping 18223 matching lines @@
     if (Smi::IsValid(value)) {
       // This cast is safe because Smi::IsValid verifies that value will fit.
       intptr_t val = static_cast<intptr_t>(value);
       return Smi::New(val);
     }
     return Mint::New(value);
   }
   return raw();
 }
 
-const char* Integer::ToHexCString(Zone* zone) const {
-  ASSERT(IsSmi() || IsMint());  // Bigint has its own implementation.
-  int64_t value = AsInt64Value();
-  if (value < 0) {
-    return OS::SCreate(zone, "-0x%" PRIX64, static_cast<uint64_t>(-value));
-  } else {
-    return OS::SCreate(zone, "0x%" PRIX64, static_cast<uint64_t>(value));
-  }
-}
-
 RawInteger* Integer::ArithmeticOp(Token::Kind operation,
                                   const Integer& other,
                                   Heap::Space space) const {
   // In 32-bit mode, the result of any operation between two Smis will fit in a
   // 32-bit signed result, except the product of two Smis, which will be 64-bit.
   // In 64-bit mode, the result of any operation between two Smis will fit in a
   // 64-bit signed result, except the product of two Smis (see below).
   if (IsSmi() && other.IsSmi()) {
     const intptr_t left_value = Smi::Value(Smi::RawCast(raw()));
     const intptr_t right_value = Smi::Value(Smi::RawCast(other.raw()));
@@ skipping 4282 matching lines @@
   }
   return UserTag::null();
 }
 
 const char* UserTag::ToCString() const {
   const String& tag_label = String::Handle(label());
   return tag_label.ToCString();
 }
 
 }  // namespace dart