Move flag count retrieval to a helper function

Move the flag count to a helper which is easier to test and re-use.

src/sidebar/annotation-metadata.js

@@ -180,9 +180,21 @@ function location(annotation) {
   return Number.POSITIVE_INFINITY;
 }
 
+/**
+ * Return the number of times the annotation has been flagged
+ * by other users. If moderation data is unavailable, returns 0.
+ */
+function flagCount(ann) {
+  if (!ann.moderation) {
+    return 0;
+  }
+  return ann.moderation.flag_count;
+}
+
 module.exports = {
   documentMetadata: documentMetadata,
   domainAndTitle: domainAndTitle,
+  flagCount: flagCount,
   isAnnotation: isAnnotation,
   isNew: isNew,
   isOrphan: isOrphan,

src/sidebar/components/moderation-banner.js

@@ -7,11 +7,7 @@ function ModerationBannerController(annotationUI, flash, store) {
   var self = this;
 
   this.flagCount = function () {
-    var moderation = self.annotation.moderation;
-    if (!moderation) {
-      return 0;
-    }
-    return moderation.flag_count;
+    return annotationMetadata.flagCount(self.annotation);
   };
 
   this.isHidden = function () {

src/sidebar/test/annotation-metadata-test.js

@@ -316,4 +316,17 @@ describe('annotation-metadata', function () {
       assert.isFalse(isWaitingToAnchor(pending));
     });
   });
+
+  describe('.flagCount', function () {
+    var flagCount = annotationMetadata.flagCount;
+
+    it('returns 0 if the user is not a moderator', function () {
+      assert.equal(flagCount(fixtures.defaultAnnotation()), 0);
+    });
+
+    it('returns the flag count if present', function () {
+      var ann = fixtures.moderatedAnnotation({ flagCount: 10});
+      assert.equal(flagCount(ann), 10);
+    });
+  });
 });