Don't spellcheck chrome://flags search box.

Bug: 907791
Change-Id: I18f62b564509ac97d54aa6fec33d213ebf16e575
Reviewed-on: https://chromium-review.googlesource.com/c/1357018Reviewed-by: Esmael El-Moslimany <aee@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612757}

components/flags_ui/resources/flags.html

@@ -23,7 +23,8 @@
   <div class="flex-container">
     <div class="flex">
       <div class="search-container">
-        <input type="text" id="search" placeholder="Search flags" tabindex="1" autocomplete="off">
+        <input type="text" id="search" placeholder="Search flags" tabindex="1"
+            autocomplete="off" spellcheck="false">
         <button class="clear-search" title="Clear search" tabindex="2"></button>
       </div>
     </div>