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

runtime/vm/intrinsifier_mips.cc

Index: runtime/vm/intrinsifier_mips.cc
diff --git a/runtime/vm/intrinsifier_mips.cc b/runtime/vm/intrinsifier_mips.cc
index 748f06dff9d7bdda74aa590ac74a56fae2844ae1..a153f456d7368e3d3e6b1360cfaf1c5d1379783c 100644
--- a/runtime/vm/intrinsifier_mips.cc
+++ b/runtime/vm/intrinsifier_mips.cc
@@ -703,12 +703,13 @@ void Intrinsifier::Integer_equalToInteger(Assembler* assembler) {
   __ andi(CMPRES1, T1, Immediate(kSmiTagMask));
   __ bne(CMPRES1, ZR, &receiver_not_smi);  // Check receiver.
 
-  // 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.
 
   __ LoadClassId(CMPRES1, T0);
   __ BranchEqual(CMPRES1, Immediate(kDoubleCid), &fall_through);
+  __ BranchEqual(CMPRES1, Immediate(kFractionCid), &fall_through);
   __ LoadObject(V0, Bool::False());  // Smi == Mint -> false.
   __ Ret();