[omnibox] Remove button option from tab switch suggestions setting

The code has already been modified to assume this option if enabled.
This CL actually removes the option.

Bug: 780835
Change-Id: I6bc84f7eb7763136d1effc40659f65297396b7b8
Reviewed-on: https://chromium-review.googlesource.com/1033574
Commit-Queue: Kevin Bailey <krb@chromium.org>
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Cr-Commit-Position: refs/heads/master@{#554586}

chrome/browser/about_flags.cc

@@ -602,9 +602,7 @@ const FeatureEntry::Choice kForceTextDirectionChoices[] = {
 const flags_ui::FeatureEntry::Choice kOmniboxTabSwitchSuggestions[] = {
     {flags_ui::kGenericExperimentChoiceDefault, "", ""},
     {"Enabled", omnibox::kOmniboxTabSwitchSuggestionsFlag, "enabled"},
-    {"Disabled", omnibox::kOmniboxTabSwitchSuggestionsFlag, "disabled"},
-    {"Button", omnibox::kOmniboxTabSwitchSuggestionsFlag,
-     omnibox::kOmniboxTabSwitchWithButton}};
+    {"Disabled", omnibox::kOmniboxTabSwitchSuggestionsFlag, "disabled"}};
 #endif
 
 #if defined(OS_CHROMEOS)

components/omnibox/browser/omnibox_field_trial.cc

@@ -49,8 +49,6 @@ const base::Feature kOmniboxTailSuggestions{
 const char kOmniboxTabSwitchSuggestionsFlag[] =
     "omnibox-tab-switch-suggestions";
 
-const char kOmniboxTabSwitchWithButton[] = "with-button";
-
 // Feature used to enable clipboard provider, which provides the user with
 // suggestions of the URL in the user's clipboard (if any) upon omnibox focus.
 const base::Feature kEnableClipboardProvider {

components/omnibox/browser/omnibox_field_trial.h

@@ -29,7 +29,6 @@ extern const base::Feature kOmniboxRichEntitySuggestions;
 extern const base::Feature kOmniboxNewAnswerLayout;
 extern const base::Feature kOmniboxTailSuggestions;
 extern const char kOmniboxTabSwitchSuggestionsFlag[];
-extern const char kOmniboxTabSwitchWithButton[];
 extern const base::Feature kEnableClipboardProvider;
 extern const base::Feature kSearchProviderWarmUpOnFocus;
 extern const base::Feature kZeroSuggestRedirectToChrome;