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

runtime/lib/bigint.dart

Index: runtime/lib/bigint.dart
diff --git a/runtime/lib/bigint.dart b/runtime/lib/bigint.dart
index 0c562d7b730e9b3e9e4649a9636aa8d1252454cf..36a0314870bbc321a3a840d864e1d9175b740630 100644
--- a/runtime/lib/bigint.dart
+++ b/runtime/lib/bigint.dart
@@ -1259,34 +1259,34 @@ class _Bigint extends _IntegerImplementation implements int {
   // efficiency, but are not necessary for correctness. They shortcut native
   // calls that would return null because the receiver is _Bigint.
   num operator +(num other) {
-    return other._toBigintOrDouble()._addFromInteger(this);
+    return other._toBigintIfInteger()._addFromInteger(this);
   }
   num operator -(num other) {
-    return other._toBigintOrDouble()._subFromInteger(this);
+    return other._toBigintIfInteger()._subFromInteger(this);
   }
   num operator *(num other) {
-    return other._toBigintOrDouble()._mulFromInteger(this);
+    return other._toBigintIfInteger()._mulFromInteger(this);
   }
   num operator ~/(num other) {
-    return other._toBigintOrDouble()._truncDivFromInteger(this);
+    return other._toBigintIfInteger()._truncDivFromInteger(this);
   }
   num operator %(num other) {
-    return other._toBigintOrDouble()._moduloFromInteger(this);
+    return other._toBigintIfInteger()._moduloFromInteger(this);
   }
   int operator &(int other) {
-    return other._toBigintOrDouble()._bitAndFromInteger(this);
+    return other._toBigintIfInteger()._bitAndFromInteger(this);
   }
   int operator |(int other) {
-    return other._toBigintOrDouble()._bitOrFromInteger(this);
+    return other._toBigintIfInteger()._bitOrFromInteger(this);
   }
   int operator ^(int other) {
-    return other._toBigintOrDouble()._bitXorFromInteger(this);
+    return other._toBigintIfInteger()._bitXorFromInteger(this);
   }
   int operator >>(int other) {
-    return other._toBigintOrDouble()._shrFromInt(this);
+    return other._toBigintIfInteger()._shrFromInt(this);
   }
   int operator <<(int other) {
-    return other._toBigintOrDouble()._shlFromInt(this);
+    return other._toBigintIfInteger()._shlFromInt(this);
   }
   // End of operator shortcuts.