Fraction class prototype and test (not to be committed).

runtime/vm/intrinsifier_x64.cc

Index: runtime/vm/intrinsifier_x64.cc
diff --git a/runtime/vm/intrinsifier_x64.cc b/runtime/vm/intrinsifier_x64.cc
index cdb11df87889566bef98ccde1b8fa09180d47a1d..3837aa5f6d3ecde070ea89e266e195ae757fb443 100644
--- a/runtime/vm/intrinsifier_x64.cc
+++ b/runtime/vm/intrinsifier_x64.cc
@@ -660,11 +660,14 @@ void Intrinsifier::Integer_equalToInteger(Assembler* assembler) {
   __ testq(RAX, Immediate(kSmiTagMask));
   __ j(NOT_ZERO, &receiver_not_smi);
 
-  // Left (receiver) is Smi, return false if right is not Double.
+  // Left (receiver) is Smi, return false if right is not Double or Fraction.
   // Note that an instance of Mint or Bigint never contains a value that can be
   // represented by Smi.
   __ movq(RAX, Address(RSP, + kArgumentOffset * kWordSize));
-  __ CompareClassId(RAX, kDoubleCid);
+  __ LoadClassId(TMP, RAX);
+  __ cmpl(TMP, Immediate(kDoubleCid));
+  __ j(EQUAL, &fall_through);
+  __ cmpl(TMP, Immediate(kFractionCid));
   __ j(EQUAL, &fall_through);
   __ LoadObject(RAX, Bool::False());
   __ ret();