dart2js: Don't emit static const fields since they are inlined where they are used

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

Index: sdk/lib/_internal/compiler/implementation/compile_time_constants.dart
diff --git a/sdk/lib/_internal/compiler/implementation/compile_time_constants.dart b/sdk/lib/_internal/compiler/implementation/compile_time_constants.dart
index 3f1313affdcb2f339dd10161ca8c06aee99abab0..691cbac7af90626a3cefc568083922309a361414 100644
--- a/sdk/lib/_internal/compiler/implementation/compile_time_constants.dart
+++ b/sdk/lib/_internal/compiler/implementation/compile_time_constants.dart
@@ -229,7 +229,9 @@ class ConstantHandler extends CompilerTask {
     return initialVariableValues.keys.where((element) {
       return element.kind == ElementKind.FIELD
           && !element.isInstanceMember()
-          && !element.modifiers.isFinal();
+          && !element.modifiers.isFinal()
+          // The const fields are all either emitted elsewhere or inlined.
+          && !element.modifiers.isConst();
     });
   }