Minor type inference fixes to do with null and bottom types.

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

Index: pkg/front_end/testcases/inference/coerce_bottom_and_null_types.dart.strong.expect
diff --git a/pkg/front_end/testcases/inference/coerce_bottom_and_null_types.dart.strong.expect b/pkg/front_end/testcases/inference/coerce_bottom_and_null_types.dart.strong.expect
new file mode 100644
index 0000000000000000000000000000000000000000..13b155bf484fd2c571ef34a21fe5bce8dcdd0166
--- /dev/null
+++ b/pkg/front_end/testcases/inference/coerce_bottom_and_null_types.dart.strong.expect
@@ -0,0 +1,22 @@
+library test;
+import self as self;
+import "dart:core" as core;
+
+static method f() → dynamic {
+  core::int a = 0;
+  dynamic b = null;
+  dynamic c = throw "foo";
+  () → core::int d = () → core::int => 0;
+  () → dynamic e = () → dynamic => null;
+  () → <BottomType>f = () → <BottomType>=> throw "foo";
+  () → core::int g = () → core::int {
+    return 0;
+  };
+  () → core::Null h = () → core::Null {
+    return null;
+  };
+  () → <BottomType>i = () → <BottomType>{
+    return throw "foo";
+  };
+}
+static method main() → dynamic {}