Make ~/, round, ceil, floor, truncate return ints. Remove toInt.

runtime/lib/integers.dart

Index: runtime/lib/integers.dart
diff --git a/runtime/lib/integers.dart b/runtime/lib/integers.dart
index 2b3a1ee768fd8204de05ef5eea9c8cb35ae3f9c9..d39d733219e121e1d72e71b49e9054b512c3dca6 100644
--- a/runtime/lib/integers.dart
+++ b/runtime/lib/integers.dart
@@ -114,7 +114,7 @@ class _IntegerImplementation {
       } else {
         // If abs(other) > MAX_EXACT_INT_TO_DOUBLE, then other has an integer
         // value (no bits below the decimal point).
-        other = d.toInt();
+        other = d.truncate();
       }
     }
     if (this < other) {
@@ -155,7 +155,6 @@ class _IntegerImplementation {
     return this;
   }
 
-  int toInt() { return this; }
   double toDouble() { return new _Double.fromInteger(this); }
 
   int pow(int exponent) {
@@ -164,7 +163,7 @@ class _IntegerImplementation {
       // Use Bigint instead.
       throw "_IntegerImplementation.pow not implemented for large integers.";
     }
-    return res.toInt();
+    return res.truncate();
   }
 
   String toStringAsFixed(int fractionDigits) {