Auto-expand direct linked annotations

When direct-linking to an annotation or a reply to one, auto-expand the
annotation thread to make it easier for the user to follow the whole
conversation around it.

h/static/scripts/annotation-ui.js

@@ -44,7 +44,7 @@ function initialState(settings) {
     // present in the map, the default state is used which depends on whether
     // the annotation is a top-level annotation or a reply, whether it is
     // selected and whether it matches the current filter.
-    expanded: {},
+    expanded: initialSelection(settings) || {},
 
     // Set of IDs of annotations that have been explicitly shown
     // by the user even if they do not match the current search filter

h/static/scripts/test/annotation-ui-test.js

@@ -16,6 +16,7 @@ describe('annotationUI', function () {
   describe('initialization', function () {
     it('does not set a selection when settings.annotations is null', function () {
       assert.isFalse(annotationUI.hasSelectedAnnotations());
+      assert.equal(Object.keys(annotationUI.getState().expanded).length, 0);
     });
 
     it('sets the selection when settings.annotations is set', function () {
@@ -24,6 +25,13 @@ describe('annotationUI', function () {
         testid: true,
       });
     });
+
+    it('expands the selected annotations when settings.annotations is set', function () {
+      annotationUI = annotationUIFactory({annotations: 'testid'});
+      assert.deepEqual(annotationUI.getState().expanded, {
+        testid: true,
+      });
+    });
   });
 
   describe('#addAnnotations()', function () {