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

pkg/compiler/lib/src/js_emitter/interceptor_stub_generator.dart

Index: pkg/compiler/lib/src/js_emitter/interceptor_stub_generator.dart
diff --git a/pkg/compiler/lib/src/js_emitter/interceptor_stub_generator.dart b/pkg/compiler/lib/src/js_emitter/interceptor_stub_generator.dart
index 3d3270c4de2fd8c4b765c7c24507fffd5015d213..73eeeb74b7917fba7b716820b0f270efaefe152a 100644
--- a/pkg/compiler/lib/src/js_emitter/interceptor_stub_generator.dart
+++ b/pkg/compiler/lib/src/js_emitter/interceptor_stub_generator.dart
@@ -246,7 +246,7 @@ class InterceptorStubGenerator {
       // checked mode, so we don't optimize the interceptor if the
       // compiler has type assertions enabled.
       if (selector.isIndexSet
-          && (compiler.enableTypeAssertions || !containsArray)) {
+          && (compiler.options.enableTypeAssertions || !containsArray)) {
         return null;
       }
       if (!containsArray && !containsString) {