Implementation of null-aware operators.

pkg/compiler/lib/src/dart2js.dart

Index: pkg/compiler/lib/src/dart2js.dart
diff --git a/pkg/compiler/lib/src/dart2js.dart b/pkg/compiler/lib/src/dart2js.dart
index 5469e39dc07d37632abcb02073fed8a9ac40c342..ac9de672d50ee32d8654526eea8e5e990c9facb0 100644
--- a/pkg/compiler/lib/src/dart2js.dart
+++ b/pkg/compiler/lib/src/dart2js.dart
@@ -349,6 +349,12 @@ Future<api.CompilationResult> compile(List<String> argv) {
           "Async-await is supported by default.",
           api.Diagnostic.HINT);
     }),
+    new OptionHandler('--enable-null-aware-operators', (_) {

[Siggi Cherem (dart-lang), 2015/05/22 03:50:49]

FYI - I'm adding this for now because the language tests are passing this flag
automatically (the analyzer doesn't have this feature on by default) 

[Johnni Winther, 2015/05/22 12:39:48]

I thought that experimental features should be opt-in.

[Siggi Cherem (dart-lang), 2015/05/22 19:49:54]

Oh - I thought that because the DEP was accepted and changes are drafted in the
spec, that this was no longer experimental :), but maybe it's worth waiting
until the VM has it in.

I changed it to be an error in the scanner if this option is missing.

+      diagnosticHandler.info(
+          "Option '--enable-null-aware-operators' is not needed. "
+          "Null aware operators are supported by default.",
+          api.Diagnostic.HINT);
+    }),
     new OptionHandler('--enable-enum', (_) {
       diagnosticHandler.info(
           "Option '--enable-enum' is no longer needed. "