Switch the order of the "display"/"print" intent handling in XfaLayerBuilder.render

Given that the "print"-intent is special, and that we should always fallback to the "display"-intent, let's ensure that the code actually reflects that.
Also, ensure that the method always returns a `Promise` since that's what the documentation says.

web/xfa_layer_builder.js

@@ -43,7 +43,27 @@ class XfaLayerBuilder {
    *   annotations is complete.
    */
   render(viewport, intent = "display") {
-    if (intent === "display") {
+    if (intent === "print") {
+      viewport.dontFlip = true;
+      const parameters = {
+        viewport,
+        div: this.div,
+        xfa: this.xfaHtml,
+        page: null,
+        annotationStorage: this.annotationStorage,
+        intent,
+      };
+
+      // Create an xfa layer div and render the form
+      const div = document.createElement("div");
+      this.pageDiv.appendChild(div);
+      parameters.div = div;
+
+      XfaLayer.render(parameters);
+      return Promise.resolve();
+    }
+
+    // intent === "display"
     return this.pdfPage
       .getXfa()
       .then(xfa => {
@@ -74,27 +94,6 @@ class XfaLayerBuilder {
       });
   }
 
-    // intent === "print".
-    viewport.dontFlip = true;
-    const parameters = {
-      viewport,
-      div: this.div,
-      xfa: this.xfaHtml,
-      page: null,
-      annotationStorage: this.annotationStorage,
-      intent,
-    };
-
-    // Create an xfa layer div and render the form
-    const div = document.createElement("div");
-    this.pageDiv.appendChild(div);
-    parameters.div = div;
-
-    XfaLayer.render(parameters);
-
-    return null;
-  }
-
   cancel() {
     this._cancelled = true;
   }