Added basic browser test for window.print() from Chrome apps.

chrome/browser/resources/print_preview/native_layer.js

Index: chrome/browser/resources/print_preview/native_layer.js
diff --git a/chrome/browser/resources/print_preview/native_layer.js b/chrome/browser/resources/print_preview/native_layer.js
index bda89a709ea50dee81146b91d68e56257de5e08d..93292e9e7191115e4829649ed56f8296ad5998f3 100644
--- a/chrome/browser/resources/print_preview/native_layer.js
+++ b/chrome/browser/resources/print_preview/native_layer.js
@@ -40,6 +40,8 @@ cr.define('print_preview', function() {
     global['printScalingDisabledForSourcePDF'] =
         this.onPrintScalingDisabledForSourcePDF_.bind(this);
     global['onDidGetAccessToken'] = this.onDidGetAccessToken_.bind(this);
+    global['autoCancelPrintPreviewForTesting'] =
+        this.autoCancelPrintPreviewForTesting_.bind(this);
   };
 
   /**
@@ -49,6 +51,8 @@ cr.define('print_preview', function() {
    */
   NativeLayer.EventType = {
     ACCESS_TOKEN_READY: 'print_preview.NativeLayer.ACCESS_TOKEN_READY',
+    AUTO_CANCEL_FOR_TESTING:
+      'print_preview.NativeLayer.AUTO_CANCEL_FOR_TESTING',
     CAPABILITIES_SET: 'print_preview.NativeLayer.CAPABILITIES_SET',
     CLOUD_PRINT_ENABLE: 'print_preview.NativeLayer.CLOUD_PRINT_ENABLE',
     DESTINATIONS_RELOAD: 'print_preview.NativeLayer.DESTINATIONS_RELOAD',
@@ -577,6 +581,16 @@ cr.define('print_preview', function() {
      */
     onPrintScalingDisabledForSourcePDF_: function() {
       cr.dispatchSimpleEvent(this, NativeLayer.EventType.DISABLE_SCALING);
+    },
+
+    /**
+     * Cancel the preview and close the preview dialog. This function is called
+     * from C++ testing code.
+     * @private
+     */
+    autoCancelPrintPreviewForTesting_: function() {
+      cr.dispatchSimpleEvent(
+          this, NativeLayer.EventType.AUTO_CANCEL_FOR_TESTING);
     }
   };