Makes dialog print on ENTER key press.

chrome/browser/resources/print_preview/print_preview.js

Index: chrome/browser/resources/print_preview/print_preview.js
diff --git a/chrome/browser/resources/print_preview/print_preview.js b/chrome/browser/resources/print_preview/print_preview.js
index dd82dfc8e4ce7b76cc805aa4df2a9fa95246161c..fe7c035c3437816f4b714cfe0dd04dd6542bb9ce 100644
--- a/chrome/browser/resources/print_preview/print_preview.js
+++ b/chrome/browser/resources/print_preview/print_preview.js
@@ -657,6 +657,14 @@ cr.define('print_preview', function() {
         }
       }
 
+      if (e.keyCode == 13 /*enter*/ && this.printTicketStore_.isTicketValid()) {
+        assert(this.uiState_ == PrintPreview.UiState_.READY,
+          'Trying to print when not in ready state: ' + this.uiState_);
+        this.printDocumentOrOpenPdfPreview_(false /*isPdfPreview*/);
+        e.preventDefault();
+        return;
+      }
+
       // Pass certain directional keyboard events to the PDF viewer.
       this.previewArea_.handleDirectionalKeyEvent(e);
     },