[Mac] Add Text Suggestions Touch Bar to Experimental UI

Enabling the experimental UI flag, chrome://flags#upcoming-ui-features,
will now enable the text suggestions touch bar.

Bug: 717553
Change-Id: Ib78dc1298d548bd3548441667ab4f46e62f3b98a
Reviewed-on: https://chromium-review.googlesource.com/1167800
Commit-Queue: Tessa Nijssen <tnijssen@google.com>
Commit-Queue: Avi Drissman <avi@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Sarah Chan <spqchan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581685}

chrome/browser/ui/cocoa/touchbar/web_textfield_touch_bar_controller.mm

@@ -44,7 +44,8 @@
   if ((self = [super init])) {
     controller_ = controller;
 
-    if (base::FeatureList::IsEnabled(features::kTextSuggestionsTouchBar)) {
+    if (base::FeatureList::IsEnabled(features::kTextSuggestionsTouchBar) ||
+        base::FeatureList::IsEnabled(features::kExperimentalUi)) {
       textSuggestionsTouchBarController_.reset(
           [[TextSuggestionsTouchBarController alloc]
               initWithWebContents:[controller_ webContents]