[MD settings] idle load basic and advanced pages

chrome/test/data/webui/settings/settings_page_browsertest.js

Index: chrome/test/data/webui/settings/settings_page_browsertest.js
diff --git a/chrome/test/data/webui/settings/settings_page_browsertest.js b/chrome/test/data/webui/settings/settings_page_browsertest.js
index a1c5ef5426d0656bc5cccf3cf418020abd98521f..52b1fb3f5c9259b22f85c19866979962a3cad4f3 100644
--- a/chrome/test/data/webui/settings/settings_page_browsertest.js
+++ b/chrome/test/data/webui/settings/settings_page_browsertest.js
@@ -62,6 +62,11 @@ SettingsPageBrowserTest.prototype = {
     var pageType = 'settings-' + type + '-page';
     var page = settingsMain.$$(pageType);
     assertTrue(!!page);
+    var idleRender = page.$$('template[is=settings-idle-render]');
+    if (idleRender) {
+      idleRender.get();
+      Polymer.dom.flush();
+    }
     return page;

[michaelpg, 2017/02/01 07:53:50]

add a comment that getting the basic page force-renders the advanced page

(why are these test-behavioral changes needed if the current advanced page is
already wrapped in a dom-if?)

[dschuyler, 2017/02/01 21:52:31]

Whether the contents are hidden or not is controlled within the
settings-idle-render. This get() dose not change the hidden attribute on the
contents.

[michaelpg, 2017/02/02 00:00:35]

The contents might not exist before get(). So getPage can now create the
Advanced page by triggering settings-idle-render to render, which AFAICT is
entirely new behavior by this function. Not concerned whether it's hidden.

Take testSubPages/testSubPage in settings_subpage_browsertest.js as an example.
Previously we would test each Basic section without the Advanced sections even
existing. Now they will exist (but be hidden maybe) which no longer reflects how
the page actually loads.

[dschuyler, 2017/02/02 02:28:15]

testSubPages/testSubPage appear to be measuring the performance rather than
testing the subpages (maybe it could be timeSubPages instead?)

The idle time expansion will expand the dom that holds the subpages. It doesn't
actually expand the subpages. IMO, the testSubPages/testSubPage remain as valid
with this CL (or without it). If there were an unexpected change in the timing
results, they could be acknowledged/accounted for.

Aside from the explanation above, it's worth considering that this will be the
way pages are loaded after this CL lands. So it will reflect the way pages are
loaded at that time.

   },