Wrap parens around anonymous classes if first in statement

lib/output.js

@@ -629,6 +629,15 @@ function OutputStream(options) {
         return false;
     });
 
+    // Anonymous classes needs parens around when it's the first token in a statement.
+    PARENS(AST_Class, function(output){
+        if (this.name === undefined && first_in_statement(output)) {
+            return true;
+        }
+
+        return false;
+    });
+
     PARENS(AST_Arrow, function(output){
         var p = output.parent();
         return p instanceof AST_PropAccess && p.expression === this;

test/compress/harmony.js

@@ -159,6 +159,17 @@ classes_with_expression_as_expand: {
     expect_exact: "class D extends(calls++,C){}"
 }
 
+class_as_sequence_expression: {
+    options = {
+        side_effects: true
+    }
+    input: {
+        0, class {}
+        0, class A{}
+    }
+    expect_exact: "(class{});class A{};"
+}
+
 new_target: {
     input: {
         new.target;