Enable iOS most-visited zero suggest by default.

This feature was approved for launch in M65.

Bug: 787067
Change-Id: I1327a793206748537d4efeecf706c967635f17af
Reviewed-on: https://chromium-review.googlesource.com/1017901Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Justin Donnelly <jdonnelly@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553137}

components/omnibox/browser/omnibox_field_trial.cc

@@ -139,7 +139,7 @@ const base::Feature kBreakWordsAtUnderscores{"OmniboxBreakWordsAtUnderscores",
 #if defined(OS_IOS)
 // Feature used to enable ZeroSuggestProvider on iOS.
 const base::Feature kZeroSuggestProviderIOS{"ZeroSuggestProviderIOS",
-                                            base::FEATURE_DISABLED_BY_DEFAULT};
+                                            base::FEATURE_ENABLED_BY_DEFAULT};
 #endif
 
 }  // namespace omnibox