Remove reference to compiler from libary loader, fix analyzer warning

pkg/compiler/lib/src/js_backend/no_such_method_registry.dart

Index: pkg/compiler/lib/src/js_backend/no_such_method_registry.dart
diff --git a/pkg/compiler/lib/src/js_backend/no_such_method_registry.dart b/pkg/compiler/lib/src/js_backend/no_such_method_registry.dart
index 678f805a9edb0f35a0afd589d6bf3a765fe33225..4cbc011d7dfe48394a5830a0cd8db570f9fc4a5c 100644
--- a/pkg/compiler/lib/src/js_backend/no_such_method_registry.dart
+++ b/pkg/compiler/lib/src/js_backend/no_such_method_registry.dart
@@ -206,11 +206,12 @@ class NoSuchMethodRegistry {
         expr = stmt.expression;
       }
     }
-    if (expr is Send &&
-        expr.isTypeCast &&
-        expr.typeAnnotationFromIsCheckOrCast.typeName is Identifier &&
-        expr.typeAnnotationFromIsCheckOrCast.typeName.source == "dynamic") {
-      expr = (expr as Send).receiver;
+    if (expr is Send && expr.isTypeCast) {
+      Send sendExpr = expr;
+      var typeName = sendExpr.typeAnnotationFromIsCheckOrCast.typeName;
+      if (typeName is Identifier && typeName.source == "dynamic") {
+        expr = sendExpr.receiver;
+      }
     }
     if (expr is Send &&
         expr.isSuperCall &&