[MD settings] handle being detached on cr-lazy-render and settings-idle-render

chrome/test/data/webui/cr_elements/cr_elements_browsertest.js

Index: chrome/test/data/webui/cr_elements/cr_elements_browsertest.js
diff --git a/chrome/test/data/webui/cr_elements/cr_elements_browsertest.js b/chrome/test/data/webui/cr_elements/cr_elements_browsertest.js
index 1fcc2225f3cfa25392e7294adfffcc6f965c5c19..a3fd33d0039bae84205c000facc4ccaf28e6beec 100644
--- a/chrome/test/data/webui/cr_elements/cr_elements_browsertest.js
+++ b/chrome/test/data/webui/cr_elements/cr_elements_browsertest.js
@@ -48,6 +48,7 @@ CrElementsLazyRenderTest.prototype = {
 
   /** @override */
   extraLibraries: CrElementsBrowserTest.prototype.extraLibraries.concat([
+    ROOT_PATH + 'ui/webui/resources/js/assert.js',

[Dan Beam, 2017/02/08 05:31:36]

please don't add dependencies for production code in tests only.

please, instead, add a <link rel="import"
href="chrome://resources/html/assert.html"> in settings_idle_render.html

backstory: dpapad@ and I had to remove a bunch of "only load this file in tests"
via importHtml(), loadScript(), and extraLibraries because folks were adding
dependencies only in tests when they should just be included in the code that
uses them.

[dschuyler, 2017/02/09 00:42:47]

Thanks. With the other note about detached settings-idle-render having .get()
called, I found that the asserts no longer applied.

     'cr_lazy_render_tests.js'
   ]),
 };