Set autocomplete type on search field in chrome://flags

That field should not get autocomplete suggestions.

Change-Id: Ie711c8d15cffb612e55dfcc057db8a7a4ef8eb19
Reviewed-on: https://chromium-review.googlesource.com/1156912Reviewed-by: Grace Kloba <klobag@chromium.org>
Commit-Queue: Sebastien Seguin-Gagnon <sebsg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580881}

components/flags_ui/resources/flags.html

@@ -23,7 +23,7 @@
   <div class="flex-container">
     <div class="flex">
       <div class="search-container">
-        <input type="text" id="search" placeholder="Search flags" tabindex="1">
+        <input type="text" id="search" placeholder="Search flags" tabindex="1" autocomplete="search">
         <button class="clear-search" title="Clear search" tabindex="2"></button>
       </div>
     </div>