Fix top level type inference for binary operators.

pkg/front_end/testcases/inference/infer_binary_int_double.dart.strong.expect

+library test;
+import self as self;
+import "dart:core" as core;
+
+static field core::bool a_equal = 1.{core::num::==}(2.0);
+static field core::bool a_notEqual = !1.{core::num::==}(2.0);
+static field core::double a_add = 1.{core::num::+}(2.0);
+static field core::double a_subtract = 1.{core::num::-}(2.0);
+static field core::double a_multiply = 1.{core::num::*}(2.0);
+static field core::double a_divide = 1.{core::num::/}(2.0);
+static field core::int a_floorDivide = 1.{core::num::~/}(2.0);
+static field core::bool a_greater = 1.{core::num::>}(2.0);
+static field core::bool a_less = 1.{core::num::<}(2.0);
+static field core::bool a_greaterEqual = 1.{core::num::>=}(2.0);
+static field core::bool a_lessEqual = 1.{core::num::<=}(2.0);
+static field core::double a_modulo = 1.{core::num::%}(2.0);
+static method main() → dynamic {
+  self::a_equal;
+  self::a_notEqual;
+  self::a_add;
+  self::a_subtract;
+  self::a_multiply;
+  self::a_divide;
+  self::a_floorDivide;
+  self::a_greater;
+  self::a_less;
+  self::a_greaterEqual;
+  self::a_lessEqual;
+  self::a_modulo;
+}