A11y - Keyboard focus moves only to interactive elements on Dashboard

1. Remove tabindex on gr-change-list to make it not keyboard focusable
2. Set tabindex only on selected gr-change-list-item to continue
functionality of using enter to go to selected change, but make other
gr-change-list-items not keyboard focusable
3. Remove css `.content a`, since it made `a` a block and `outline`
didn’t work when `a` focused. The same css rules are in .content
and after removal page works and looks the same.

Change-Id: Ica3f279623506c847f058674ecf9defb41c1ba31
diff --git a/polygerrit-ui/app/elements/change-list/gr-change-list-item/gr-change-list-item_html.js b/polygerrit-ui/app/elements/change-list/gr-change-list-item/gr-change-list-item_html.js
index b31ab9b..f29c8bf 100644
--- a/polygerrit-ui/app/elements/change-list/gr-change-list-item/gr-change-list-item_html.js
+++ b/polygerrit-ui/app/elements/change-list/gr-change-list-item/gr-change-list-item_html.js
@@ -45,13 +45,6 @@
       white-space: nowrap;
       width: 100%;
     }
-    .content a {
-      display: block;
-      overflow: hidden;
-      text-overflow: ellipsis;
-      white-space: nowrap;
-      width: 100%;
-    }
     .comments,
     .reviewers {
       white-space: nowrap;
diff --git a/polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list.js b/polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list.js
index bd78ae9..baf9920 100644
--- a/polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list.js
+++ b/polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list.js
@@ -168,7 +168,6 @@
   /** @override */
   ready() {
     super.ready();
-    this._ensureAttribute('tabindex', 0);
     this.$.restAPI.getConfig().then(config => {
       this._config = config;
     });
@@ -296,6 +295,11 @@
     return idx == selectedIndex;
   }
 
+  _computeTabIndex(sectionIndex, index, selectedIndex) {
+    return this._computeItemSelected(sectionIndex, index, selectedIndex)
+      ? 0 : undefined;
+  }
+
   _computeItemNeedsReview(account, change, showReviewedState) {
     return showReviewedState && !change.reviewed &&
         !change.work_in_progress &&
diff --git a/polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list_html.js b/polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list_html.js
index f7c50e6..2e50cd8 100644
--- a/polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list_html.js
+++ b/polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list_html.js
@@ -138,7 +138,7 @@
             visible-change-table-columns="[[visibleChangeTableColumns]]"
             show-number="[[showNumber]]"
             show-star="[[showStar]]"
-            tabindex="0"
+            tabindex$="[[_computeTabIndex(sectionIndex, index, selectedIndex)]]"
             label-names="[[labelNames]]"
           ></gr-change-list-item>
         </template>