Es6ExtractClasses: correct use of ExpressionDecomposer

ExpressionDecomposer.maybeExposeExpression() guarantees that the
expression is fully exposed and should be used instead of
ExpressionDecomposer.exposeExpression().

PiperOrigin-RevId: 321810429

Author: brad4d

src/com/google/javascript/jscomp/Es6ExtractClasses.java

@@ -179,7 +179,7 @@ private boolean shouldExtractClass(Node classNode) {
 
   private void extractClass(NodeTraversal t, Node classNode) {
     if (expressionDecomposer.canExposeExpression(classNode) == DecompositionType.DECOMPOSABLE) {
-      expressionDecomposer.exposeExpression(classNode);
+      expressionDecomposer.maybeExposeExpression(classNode);
     }
     Node parent = classNode.getParent();