Toggle left diff on Shift+A

Feature: Issue 3926
Change-Id: Ia52334f2aefeae4b3f115e5779da3b61af25ba11
diff --git a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.js b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.js
index 1c56c40..a0fd8b2 100644
--- a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.js
+++ b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.js
@@ -496,10 +496,10 @@
 
       switch (e.keyCode) {
         case 65:  // 'a'
-          if (!this._loggedIn) { return; }
-
-          e.preventDefault();
-          this._openReplyDialog();
+          if (this._loggedIn && !e.shiftKey) {
+            e.preventDefault();
+            this._openReplyDialog();
+          }
           break;
         case 85:  // 'u'
           e.preventDefault();