fix resetFavicon so that it actually resets

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

@@ -393,8 +393,9 @@ export const setFavicon = (faviconPath) => {
 
 export const resetFavicon = () => {
   const faviconEl = document.getElementById('favicon');
-  const originalFavicon = faviconEl ? faviconEl.getAttribute('href') : null;
+
   if (faviconEl) {
+    const originalFavicon = faviconEl.getAttribute('data-default-href');
     faviconEl.setAttribute('href', originalFavicon);
   }
 };

app/views/layouts/_head.html.haml

@@ -25,7 +25,7 @@
   %title= page_title(site_name)
   %meta{ name: "description", content: page_description }
 
-  = favicon_link_tag favicon, id: 'favicon'
+  = favicon_link_tag favicon, id: 'favicon', :'data-default-href': favicon
 
   = stylesheet_link_tag "application", media: "all"
   = stylesheet_link_tag "print",       media: "print"

spec/javascripts/lib/utils/common_utils_spec.js

@@ -395,6 +395,7 @@ describe('common_utils', () => {
       const favicon = document.createElement('link');
       favicon.setAttribute('id', 'favicon');
       favicon.setAttribute('href', 'default/favicon');
+      favicon.setAttribute('data-default-href', 'default/favicon');
       document.body.appendChild(favicon);
     });
 
@@ -413,7 +414,7 @@ describe('common_utils', () => {
     beforeEach(() => {
       const favicon = document.createElement('link');
       favicon.setAttribute('id', 'favicon');
-      favicon.setAttribute('href', 'default/favicon');
+      favicon.setAttribute('data-original-href', 'default/favicon');
       document.body.appendChild(favicon);
     });
 
@@ -421,7 +422,9 @@ describe('common_utils', () => {
       document.body.removeChild(document.getElementById('favicon'));
     });
 
-    it('should reset page favicon to tanuki', () => {
+    it('should reset page favicon to the default icon', () => {
+      const favicon = document.getElementById('favicon');
+      favicon.setAttribute('href', 'new/favicon');
       commonUtils.resetFavicon();
       expect(document.getElementById('favicon').getAttribute('href')).toEqual('default/favicon');
     });
@@ -434,6 +437,8 @@ describe('common_utils', () => {
     beforeEach(() => {
       const favicon = document.createElement('link');
       favicon.setAttribute('id', 'favicon');
+      favicon.setAttribute('href', 'null');
+      favicon.setAttribute('data-original-href', faviconDataUrl);
       document.body.appendChild(favicon);
       mock = new MockAdapter(axios);
     });
@@ -449,7 +454,7 @@ describe('common_utils', () => {
       commonUtils.setCiStatusFavicon(BUILD_URL)
         .then(() => {
           const favicon = document.getElementById('favicon');
-          expect(favicon.getAttribute('href')).toEqual('null');
+          expect(favicon.getAttribute('href')).toEqual(faviconDataUrl);
           done();
         })
         // Error is already caught in catch() block of setCiStatusFavicon,