Merge branch 'fix-hidden-discussion-permalinks' into 'master'

Automatically expand hidden discussions when accessed via a permalink hash (closes #19304)

## What does this MR do?

Addresses "Auto-expand a discussion note when we arrive via anchor" (issue #19304)

## Are there points in the code the reviewer needs to double check?

Let me know if the code is consistent with community standards (not 100% sure about indentation of chained jQuery actions)

I don't think this MR warrants any unit tests or documentation, but let me know if you disagree.  I'll add the requisite CHANGELOG entry upon approval.

## Why was this MR needed?

Currently, if a discussion is accessed via a permalink to an "outdated" diff discussion, the anchor will not bring you to the expected part of the page.

## What are the relevant issue numbers?

#19304 

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)


See merge request !5585

app/assets/javascripts/behaviors/toggler_behavior.js

-(function() {
+(function(w) {
   $(function() {
-    return $("body").on("click", ".js-toggle-button", function(e) {
-      $(this).find('i').toggleClass('fa fa-chevron-down').toggleClass('fa fa-chevron-up');
-      $(this).closest(".js-toggle-container").find(".js-toggle-content").toggle();
-      return e.preventDefault();
+    $('.js-toggle-button').on('click', function(e) {
+      e.preventDefault();
+      $(this)
+        .find('.fa')
+          .toggleClass('fa-chevron-down fa-chevron-up')
+        .end()
+        .closest('.js-toggle-container')
+          .find('.js-toggle-content')
+            .toggle()
+      ;
     });
-  });
 
-}).call(this);
+    // If we're accessing a permalink, ensure it is not inside a
+    // closed js-toggle-container!
+    var hash = w.gl.utils.getLocationHash();
+    var anchor = hash && document.getElementById(hash);
+    var container = anchor && $(anchor).closest('.js-toggle-container');
+
+    if (container && container.find('.js-toggle-content').is(':hidden')) {
+      container.find('.js-toggle-button').trigger('click');
+      anchor.scrollIntoView();
+    }
+  });
+})(window);

app/assets/javascripts/lib/utils/url_utility.js

@@ -43,7 +43,7 @@
       }
       return newUrl;
     };
-    return w.gl.utils.removeParamQueryString = function(url, param) {
+    w.gl.utils.removeParamQueryString = function(url, param) {
       var urlVariables, variables;
       url = decodeURIComponent(url);
       urlVariables = url.split('&');
@@ -59,6 +59,16 @@
         return results;
       })()).join('&');
     };
+    w.gl.utils.getLocationHash = function(url) {
+      var hashIndex;
+      if (typeof url === 'undefined') {
+        // Note: We can't use window.location.hash here because it's
+        // not consistent across browsers - Firefox will pre-decode it
+        url = window.location.href;
+      }
+      hashIndex = url.indexOf('#');
+      return hashIndex === -1 ? null : url.substring(hashIndex + 1);
+    };
   })(window);
 
 }).call(this);