MD WebUI: Center search field correctly inside cr-toolbar

ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar.html

Index: ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar.html
diff --git a/ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar.html b/ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar.html
index a50b7853ada9a5c9a7a805dcc76654b82bf82f16..5f0da9873eb708e119a1a998dae14c9b4b7f6597 100644
--- a/ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar.html
+++ b/ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar.html
@@ -21,6 +21,8 @@
       #leftContent {
         align-items: center;
         display: flex;
+        position: absolute;
+        transition: opacity 100ms;
       }
 
       #leftContent paper-icon-button {
@@ -41,12 +43,20 @@
         justify-content: center;
       }
 
+      :host(:not([narrow_])) #centeredContent {
+        /*
+         * Create a 180px area on the left which the search field will never
+         * overlap (it will go off-center to avoid it).
+         */
+        margin: 0 180px;
+      }
+
       :host([narrow_]) #centeredContent {
         justify-content: flex-end;
       }
 
       :host([narrow_][showing-search_]) #leftContent {
-        display: none;
+        opacity: 0;
       }
     </style>
     <div id="leftContent">