Don't emit unused hints when there are compilation errors.

dart/sdk/lib/_internal/compiler/implementation/compiler.dart

Index: dart/sdk/lib/_internal/compiler/implementation/compiler.dart
diff --git a/dart/sdk/lib/_internal/compiler/implementation/compiler.dart b/dart/sdk/lib/_internal/compiler/implementation/compiler.dart
index 1f23e063f50c707cbefaf22444b4a7f1636672ae..7ac0ee94a50b21e75c2580cfa99aec52da81d76e 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/compiler.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/compiler.dart
@@ -1087,6 +1087,7 @@ abstract class Compiler implements DiagnosticListener {
     processQueue(enqueuer.resolution, main);
     enqueuer.resolution.logSummary(log);
 
+    if (compilationFailed) return;
     if (analyzeOnly) {
       if (!analyzeAll) {
         // No point in reporting unused code when [analyzeAll] is true: all
@@ -1095,7 +1096,6 @@ abstract class Compiler implements DiagnosticListener {
       }
       return;
     }
-    if (compilationFailed) return;
     assert(main != null);
     phase = PHASE_DONE_RESOLVING;