Remove overflow tabs logic (no longer used)

Fix
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12198#note_37143794

app/assets/javascripts/repo/components/repo_tabs.vue

 <script>
-import Vue from 'vue';
 import Store from '../stores/repo_store';
 import RepoTab from './repo_tab.vue';
 import RepoMixin from '../mixins/repo_mixin';
@@ -14,29 +13,19 @@ const RepoTabs = {
   data: () => Store,
 
   methods: {
-    isOverflow() {
-      return this.$el.scrollWidth > this.$el.offsetWidth;
-    },
-
     xClicked(file) {
       Store.removeFromOpenedFiles(file);
     },
   },
-
-  watch: {
-    openedFiles() {
-      Vue.nextTick(() => {
-        this.tabsOverflow = this.isOverflow();
-      });
-    },
-  },
 };
 
 export default RepoTabs;
 </script>
 
 <template>
-<ul id="tabs" v-if="isMini" v-cloak :class="{'overflown': tabsOverflow}">
+<ul
+  v-if="isMini"
+  id="tabs">
   <repo-tab v-for="tab in openedFiles" :key="tab.id" :tab="tab" :class="{'active' : tab.active}" @xclicked="xClicked"/>
   <li class="tabs-divider" />
 </ul>

app/assets/javascripts/repo/stores/repo_store.js

@@ -26,7 +26,6 @@ const RepoStore = {
   tabSize: 100,
   defaultTabSize: 100,
   minTabSize: 30,
-  tabsOverflow: 41,
   submitCommitsLoading: false,
   binaryLoaded: false,
   dialog: {

spec/javascripts/repo/components/repo_tabs_spec.js

@@ -18,13 +18,11 @@ describe('RepoTabs', () => {
 
   it('renders a list of tabs', () => {
     RepoStore.openedFiles = openedFiles;
-    RepoStore.tabsOverflow = true;
 
     const vm = createComponent();
     const tabs = [...vm.$el.querySelectorAll(':scope > li')];
 
     expect(vm.$el.id).toEqual('tabs');
-    expect(vm.$el.classList.contains('overflown')).toBeTruthy();
     expect(tabs.length).toEqual(3);
     expect(tabs[0].classList.contains('active')).toBeTruthy();
     expect(tabs[1].classList.contains('active')).toBeFalsy();
@@ -39,15 +37,6 @@ describe('RepoTabs', () => {
     expect(vm.$el.innerHTML).toBeFalsy();
   });
 
-  it('does not apply overflown class if not tabsOverflow', () => {
-    RepoStore.openedFiles = openedFiles;
-    RepoStore.tabsOverflow = false;
-
-    const vm = createComponent();
-
-    expect(vm.$el.classList.contains('overflown')).toBeFalsy();
-  });
-
   describe('methods', () => {
     describe('xClicked', () => {
       it('calls removeFromOpenedFiles with file obj', () => {