Add methods for creating Bigint objects from unsigned 64-bit integers.

runtime/vm/bigint_operations.h

Index: runtime/vm/bigint_operations.h
diff --git a/runtime/vm/bigint_operations.h b/runtime/vm/bigint_operations.h
index 52d8946f0dffccba40b1d07e5fe118d7b9962d12..ce2916c02d387f73fb871e92a838c8ea50e764ee 100644
--- a/runtime/vm/bigint_operations.h
+++ b/runtime/vm/bigint_operations.h
@@ -20,6 +20,8 @@ class BigintOperations : public AllStatic {
  public:
   static RawBigint* NewFromSmi(const Smi& smi, Heap::Space space = Heap::kNew);
   static RawBigint* NewFromInt64(int64_t value, Heap::Space space = Heap::kNew);
+  static RawBigint* NewFromUInt64(uint64_t value,
+                                  Heap::Space space = Heap::kNew);
   // The given string must be a valid integer representation. It may be
   // prefixed by a minus and/or "0x".
   // Returns Bigint::null() if the string cannot be parsed.
@@ -55,6 +57,10 @@ class BigintOperations : public AllStatic {
   static bool FitsIntoInt64(const Bigint& bigint);
   static int64_t ToInt64(const Bigint& bigint);
 
+  static bool FitsIntoUInt64(const Bigint& bigint);
+  static uint64_t ToUInt64(const Bigint& bigint);
+  static uint64_t AbsToUInt64(const Bigint& bigint);
+
   static RawDouble* ToDouble(const Bigint& bigint);
 
   static RawBigint* Add(const Bigint& a, const Bigint& b);