All strong mode cleaning of dart2js.

tests/compiler/dart2js/constant_expression_test.dart

Index: tests/compiler/dart2js/constant_expression_test.dart
diff --git a/tests/compiler/dart2js/constant_expression_test.dart b/tests/compiler/dart2js/constant_expression_test.dart
index 023c932220c6b6b1bb3fdca0b6f12587c2dc5b28..8be001ea3527ce69a03e88c6a534b55b78653ef4 100644
--- a/tests/compiler/dart2js/constant_expression_test.dart
+++ b/tests/compiler/dart2js/constant_expression_test.dart
@@ -210,10 +210,10 @@ Future testData(TestData data) async {
       memorySourceFiles: {'main.dart': source}, options: ['--analyze-all']);
   Compiler compiler = result.compiler;
   MemoryEnvironment environment = new MemoryEnvironment(compiler);
-  var library = compiler.frontendStrategy.elementEnvironment.mainLibrary;
+  dynamic library = compiler.frontendStrategy.elementEnvironment.mainLibrary;
   constants.forEach((String name, ConstantData data) {
     FieldElement field = library.localLookup(name);
-    var constant = field.constant;
+    dynamic constant = field.constant;
     Expect.equals(
         data.kind,
         constant.kind,