Bug 1572475 - Make the about:logins sidebar have a fixed width. r=MattN

Differential Revision: https://phabricator.services.mozilla.com/D42228

--HG--
extra : moz-landing-system : lando

browser/components/aboutlogins/content/aboutLogins.css

@@ -4,7 +4,7 @@
 
 body {
   display: grid;
-  grid-template-columns: minmax(320px, max-content) 1fr;
+  grid-template-columns: 320px 1fr;
   grid-template-rows: 75px 1fr;
   grid-template-areas: "header header"
                        "logins login";

browser/components/aboutlogins/content/aboutLogins.html

@@ -104,7 +104,7 @@
         <div class="favicon-wrapper">
           <img class="favicon" src="" alt=""/>
         </div>
-        <div>
+        <div class="labels">
           <span class="title"></span>
           <span class="username"></span>
         </div>

browser/components/aboutlogins/content/components/login-list.css

@@ -107,10 +107,14 @@ ol {
   font-weight: 600;
 }
 
+.labels {
+  flex-grow: 1;
+  overflow: hidden;
+}
+
 .title,
 .username {
   display: block;
-  max-width: 50ch;
   text-overflow: ellipsis;
   overflow: hidden;
 }