Enable strong mode in DDC, fix all warnings/errors

lib/src/compiler/type_utilities.dart

Index: lib/src/compiler/type_utilities.dart
diff --git a/lib/src/compiler/type_utilities.dart b/lib/src/compiler/type_utilities.dart
index 0614029713dd2091e1e045730f5d863a64630c12..31a5f06a2d0271d54daf2f1d648c8047a3affe5d 100644
--- a/lib/src/compiler/type_utilities.dart
+++ b/lib/src/compiler/type_utilities.dart
@@ -162,7 +162,7 @@ class TypeTable {
   /// definitions tracked by the table.  If [formals] is present, only
   /// emit the definitions which depend on the formals.
   List<JS.Statement> discharge([List<TypeParameterElement> formals]) {
-    var filter = formals?.expand((p) => _scopeDependencies[p] ?? []);
+    var filter = formals?.expand((p) => _scopeDependencies[p] ?? <DartType>[]);

[Leaf, 2016/05/26 17:53:38]

It sure would be nice if our final inference algorithm could handle this
pattern.

[Jennifer Messerly, 2016/05/26 18:11:48]

Had the same thought :)

filed https://github.com/dart-lang/sdk/issues/26552

     var stmts = [
       _cacheNames,
       _definiteCacheNames,