cros: Remove "(TEMP): Show webui button".

I am not aware of any features which still require this.

Bug: 836119
Change-Id: Id423a3dd6bafd6cbf11786a20e8e6776792ea739
Reviewed-on: https://chromium-review.googlesource.com/1131822Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Rahul Chaturvedi <rkc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579966}

ash/ash_strings.grd

@@ -183,9 +183,6 @@ This file contains the strings for ash.
       <message name="IDS_ASH_ADD_USER_BUTTON" desc="Text shown on an add user button on login/locker screen">
         Add Person
       </message>
-      <message name="IDS_ASH_SHOW_WEBUI_LOGIN_BUTTON" desc="Button on login/lock screen which reverts to the previous implementation." translateable="false">
-        (TEMP) Show webui login; if used file bug (crbug.com) or feedback (alt+shift+i)
-      </message>
       <message name="IDS_ASH_SHELF_APPS_BUTTON" desc="Text shown on apps button on login screen.">
         Apps
       </message>

ash/shelf/login_shelf_view.cc

@@ -304,8 +304,6 @@ LoginShelfView::LoginShelfView(
   add_button(kBrowseAsGuest, IDS_ASH_BROWSE_AS_GUEST_BUTTON,
              kShelfBrowseAsGuestButtonIcon);
   add_button(kAddUser, IDS_ASH_ADD_USER_BUTTON, kShelfAddPersonButtonIcon);
-  add_button(kShowWebUiLogin, IDS_ASH_SHOW_WEBUI_LOGIN_BUTTON,
-             kShelfSignOutButtonIcon);
 
   // Adds observers for states that affect the visiblity of different buttons.
   tray_action_observer_.Add(Shell::Get()->tray_action());
@@ -365,9 +363,6 @@ void LoginShelfView::GetAccessibleNodeData(ui::AXNodeData* node_data) {
 
 void LoginShelfView::ButtonPressed(views::Button* sender,
                                    const ui::Event& event) {
-  // Intentional crash. session_manager will add --show-webui-login.
-  CHECK(sender->id() != kShowWebUiLogin);
-
   UserMetricsRecorder::RecordUserClickOnShelfButton(
       GetUserClickTarget(sender->id()));
   switch (sender->id()) {

ash/shelf/login_shelf_view.h

@@ -48,7 +48,6 @@ class ASH_EXPORT LoginShelfView : public views::View,
     kCancel,          // Cancel multiple user sign-in.
     kBrowseAsGuest,   // Use in guest mode.
     kAddUser,         // Add a new user.
-    kShowWebUiLogin,  // Show webui login.
     kApps,            // Show list of available kiosk apps.
   };