Set language settings enabled as default on TOT.

We have got the approval to launch this feature from M65.
See crbug/781915. In order to set the experiment configuration to 100%,
I need to enable it on TOT first. And there will be other CLs to clean
all the experiment code.

Bug: 808935
Change-Id: I86bf02ebe847b8841d7a0b2bddde4a3bfd7a537e
Reviewed-on: https://chromium-review.googlesource.com/964108
Commit-Queue: Leo Zhang <googleo@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543629}

chrome/browser/android/chrome_feature_list.cc

@@ -283,7 +283,7 @@ const base::Feature kImprovedA2HS{"ImprovedA2HS",
                                   base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kLanguagesPreference{"LanguagesPreference",
-                                         base::FEATURE_DISABLED_BY_DEFAULT};
+                                         base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kModalPermissionDialogView{
     "ModalPermissionDialogView", base::FEATURE_DISABLED_BY_DEFAULT};