MD Settings: Migrate enable-translation toggle from non-MD settings page.

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

Index: chrome/test/data/webui/settings/languages_page_browsertest.js
diff --git a/chrome/test/data/webui/settings/languages_page_browsertest.js b/chrome/test/data/webui/settings/languages_page_browsertest.js
index a7e1dd9673e32a6dc906821bab903fb4cb14851c..0363c1738cc2452ea211a51406a5814eb488bbdd 100644
--- a/chrome/test/data/webui/settings/languages_page_browsertest.js
+++ b/chrome/test/data/webui/settings/languages_page_browsertest.js
@@ -235,6 +235,14 @@ TEST_F('SettingsLanguagesPageBrowserTest', 'MAYBE_LanguagesPage', function() {
             cr.isChromeOS || cr.isWindows ? 1 : 0, separator.offsetHeight);
       });
 
+      test('test enable translation toggle', function() {
+        var toggle = languagesPage.$.offerTranslateOtherLangs;

[michaelpg, 2017/01/31 21:54:10]

this assumes translate is already enabled. we should first set the pref (see the
test below).

[scottchen, 2017/02/01 01:02:39]

The button that this line is grabbing is the toggle to enable/disable
prefs.translate.enabled itself, which should always exist and be visible on the
page. In which case, setting the pref is not necessary, since all the test
should care about is translate.enabled is different from the initial value after
being clicked.

I think you might be thinking of a different button that only exists in the
overflow menu if translate.enabled = true (i.e. the button that is being tested
in the test below). 

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

origTranslateEnabled is used to ensure the value gets reset to the default when
we leave this test suite. It's only set once, so relying on it within a test is
fragile. If we were to change or swap some tests, the value might be different
than origTranslateEnabled when we get to this test. That's why I suggest setting
the pref first, or at least querying for the current value of the pref, before
testing the toggle.

[scottchen, 2017/02/01 02:04:31]

The test would be valid regardless of origTranslateEnabled's initial value,
because all it checks is whether or not the value is flipped. (new value != old
value); it doesn't actually check if the value is truthy or falsey, so even if
we query the current value, we'd still be testing for "new value != old value"
anyway - so I'm not sure how it'll make a difference.
(See the assertEquals line below).

So if we query for the current value, we'd be doing:

var curValue = origTranslateEnabled;
... //flip the toggle
assertEquals(!curValue, newTranslateEnabled);

which would be exactly the same as the current code, just with one extra
proxy-variable.

[michaelpg, 2017/02/01 02:57:15]

I was playing with this test to try to show what I mean, but it's behaving
weirdly. MockInteractions.tap(toggle) doesn't appear to be actually changing the
state of the toggle.

Which would explain why we're not seeing the failure I expect here.

[scottchen, 2017/02/01 18:52:35]

Acknowledged. Please see newest patch.

+        assertTrue(!!toggle);
+        MockInteractions.tap(toggle);
+        var newTranslateEnabled = languageHelper.prefs.translate.enabled.value;
+        assertEquals(!origTranslateEnabled, newTranslateEnabled);

[michaelpg, 2017/01/31 21:54:10]

can you also test that disabling the toggle button hides the menu option in a
language's dropdown? (again see test below for set-up)

[scottchen, 2017/02/01 01:02:38]

Do you mean disabling the toggle button as in <settings-toggle-button disabled>,
or do you mean disabling translation (i.e. translate.enabled = false)?

I don't think <settings-toggle-button disabled> should impact whether the menu
option show up either way, and currently there's no condition in which the
toggle would be disabled.

If you mean the latter, I agree we should test for that :) I'll add a new test
though, since it seems like a separate concern than what we're testing for here.

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

Sorry, yes, if we "uncheck" the toggle button to turn off translate
(translate.enabled = false). Thanks.

+      });
+
       test('toggle translate', function(done) {

[michaelpg, 2017/01/31 21:54:10]

change title to something like 'toggle translate for a specific language' since
it's ambiguous now

[scottchen, 2017/02/01 01:02:39]

Done.

         // Enable Translate so the menu always shows the Translate checkbox.
         languageHelper.setPrefValue('translate.enabled', true);