[runtime] Add PositiveNumberToUint32 helper to avoid double to uint roundtrip

src/conversions.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_CONVERSIONS_H_
 #define V8_CONVERSIONS_H_
 
 #include <limits>
 
 #include "src/base/logging.h"
@@ skipping 150 matching lines @@
 // integer. It has to be in the range [-2^31, 2^31 - 1].
 // We also have to check for negative 0 as it is not an Integer32.
 inline bool IsInt32Double(double value);
 
 // UInteger32 is an integer that can be represented as an unsigned 32-bit
 // integer. It has to be in the range [0, 2^32 - 1].
 // We also have to check for negative 0 as it is not a UInteger32.
 inline bool IsUint32Double(double value);
 
 // Convert from Number object to C integer.
+inline uint32_t PositiveNumberToUint32(Object* number);
 inline int32_t NumberToInt32(Object* number);
 inline uint32_t NumberToUint32(Object* number);
 inline int64_t NumberToInt64(Object* number);
 
 double StringToDouble(UnicodeCache* unicode_cache, Handle<String> string,
                       int flags, double empty_string_val = 0.0);
 
 inline bool TryNumberToSize(Object* number, size_t* result);
 
 // Converts a number into size_t.
 inline size_t NumberToSize(Object* number);
 
 // returns DoubleToString(StringToDouble(string)) == string
 bool IsSpecialIndex(UnicodeCache* unicode_cache, String* string);
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_CONVERSIONS_H_