Add policy to use system default printer

chrome/test/data/webui/print_preview/print_preview_ui_browsertest.js

Index: chrome/test/data/webui/print_preview/print_preview_ui_browsertest.js
diff --git a/chrome/test/data/webui/print_preview/print_preview_ui_browsertest.js b/chrome/test/data/webui/print_preview/print_preview_ui_browsertest.js
index f0f47db9eaebbbee9382bb7ed818d3b90e19bea0..ade5198de976ac97747e962f738045c60efd6824 100644
--- a/chrome/test/data/webui/print_preview/print_preview_ui_browsertest.js
+++ b/chrome/test/data/webui/print_preview/print_preview_ui_browsertest.js
@@ -114,3 +114,8 @@ PrintPreviewUIBrowserTest.prototype = {
     mocha.grep(new RegExp(testName + '\\b')).run();
   });
 });
+
+TEST_F('PrintPreviewUIBrowserTest', 'SystemDefaultPrinterPolicy', function() {
+  loadTimeData.overrideValues({useSystemDefaultPrinter: true});

[dpapad, 2017/06/19 17:43:37]

Can we not do this inside SystemDefaultPrinterPolicy test instead? Then we can
just add 'SystemDefaultPrinterPolicy' to the array above.

Also does this test make sense on ChromeOS? It seems that it should only run on
non-ChromeOS code.

[rbpotter, 2017/06/19 23:10:49]

It doesn't work inside the test as print preview has already been
created at that point (in setup()). The policy is only checked at
creation so it has to be set before then.

Changed it to only run on non-ChromeOS.

+  mocha.grep(new RegExp('SystemDefaultPrinterPolicy' + '\\b')).run();
+});