Move all flags to CompilerOptions (first step to stop passing the compiler to

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

Index: pkg/compiler/lib/src/js_backend/runtime_types.dart
diff --git a/pkg/compiler/lib/src/js_backend/runtime_types.dart b/pkg/compiler/lib/src/js_backend/runtime_types.dart
index bcede4565de135793adbececc67508fcfbb8e499..29aade61ee46f98c0a796572eedc472e3ca51d5e 100644
--- a/pkg/compiler/lib/src/js_backend/runtime_types.dart
+++ b/pkg/compiler/lib/src/js_backend/runtime_types.dart
@@ -300,7 +300,7 @@ class _RuntimeTypes implements RuntimeTypes {
         }
       }
     });
-    if (compiler.enableTypeAssertions) {
+    if (compiler.options.enableTypeAssertions) {
       void analyzeMethod(TypedElement method) {
         DartType memberType = method.type;
         ClassElement contextClass = Types.getClassContext(memberType);