Instead of ArrayBuffer, pass blob with printerProvider.onPrintRequested

extensions/test/data/api_test/printer_provider/request_print/test.js

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Reads a blob content.
+// @param {!Blob} blob The blob to read.
+// @param {function(?string)} callback Called with the read blob content.
+//     the content will be null on error.
+function readBlob(blob, callback) {
+  var reader = new FileReader();
+  reader.onerror = function() { callback(null); };
+  reader.onloadend = function() {
+    callback(reader.result);
+  }
+  reader.readAsText(blob)
+}
+
+// Invokes |callback| with |returnValue| and verified a subsequent callback
+// invocation throws an exception.
+function wrapPrintCallback(callback, returnValue) {
+  callback(returnValue);
+  chrome.test.assertThrows(
+      callback,
+      ['OK'],
+      'Event callback must not be called more than once.');
+}
+
 chrome.test.sendMessage('loaded', function(test) {
   chrome.test.runTests([function printTest() {
     if (test == 'NO_LISTENER') {
       chrome.test.sendMessage('ready');
       chrome.test.succeed();
       return;
     }
 
     chrome.printerProvider.onPrintRequested.addListener(function(job,
                                                                  callback) {
       chrome.test.assertFalse(!!chrome.printerProviderInternal);
       chrome.test.assertTrue(!!job);
 
-      if (test == 'IGNORE_CALLBACK') {
-        chrome.test.succeed();
-        return;
+      switch (test) {
+        case 'IGNORE_CALLBACK':
+          break;
+        case 'ASYNC_RESPONSE':
+          setTimeout(callback.bind(null, 'OK'), 0);
+          break;
+        case 'INVALID_VALUE':
+          chrome.test.assertThrows(
+              callback,
+              ['XXX'],
+              'Invalid value for argument 1. ' +
+              'Value must be one of: ' +
+              '[OK, FAILED, INVALID_TICKET, INVALID_DATA].');
+          break;
+        case 'FAILED':
+        case 'INVALID_TICKET':
+        case 'INVALID_DATA':
+          wrapPrintCallback(callback, test);
+          break;
+        case 'OK':
+          readBlob(job.document, function(content) {
+            wrapPrintCallback(callback, !!content ? 'OK' : 'INVALID_DATA');
+
+            if (content)
+              chrome.test.assertEq('bytes', content);
+
+            chrome.test.succeed();
+          });
+
+          // Test will end asynchronously.
+          return;
+        default:
+          callback('FAILED');
+          chrome.test.fail('Invalid input');
+          return;
       }
 
-      if (test == 'ASYNC_RESPONSE') {
-        setTimeout(callback.bind(null, 'OK'), 0);
-        chrome.test.succeed();
-        return;
-      }
-
-      if (test == 'INVALID_VALUE') {
-        chrome.test.assertThrows(
-            callback,
-            ['XXX'],
-            'Invalid value for argument 1. ' +
-            'Value must be one of: ' +
-            '[OK, FAILED, INVALID_TICKET, INVALID_DATA].');
-      } else {
-        chrome.test.assertTrue(test == 'OK' || test == 'FAILED' ||
-            test == 'INVALID_TICKET' || test == 'INVALID_DATA');
-        callback(test);
-      }
-
-      chrome.test.assertThrows(
-          callback,
-          [test],
-          'Event callback must not be called more than once.');
-
       chrome.test.succeed();
     });
 
     chrome.test.sendMessage('ready');
   }]);
 });