Clear the message with System Geolocation permission bubble

The Geolocation Bubble is a SimpleBubbleModel which sets a
message. When asking for System Location permission there
is no message. Therefore I set up a simple way to clear the
message and cleared it when needed.

Bug: 1051591
Change-Id: Idcfe468a5a49b961da25741550aab7f350da0586
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2393522Reviewed-by: Balazs Engedy <engedy@chromium.org>
Commit-Queue: Balazs Engedy <engedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804602}

chrome/browser/ui/content_settings/content_setting_bubble_model.cc

@@ -1350,6 +1350,7 @@ void ContentSettingGeolocationBubbleModel::OnManageButtonClicked() {
 void ContentSettingGeolocationBubbleModel::
     InitializeSystemGeolocationPermissionBubble() {
   set_title(l10n_util::GetStringUTF16(IDS_GEOLOCATION_TURNED_OFF_IN_MACOS));
+  clear_message();
   AddListItem(ContentSettingBubbleModel::ListItem(
       &vector_icons::kLocationOnIcon,
       l10n_util::GetStringUTF16(IDS_GEOLOCATION),

chrome/browser/ui/content_settings/content_setting_bubble_model.h

@@ -240,6 +240,7 @@ class ContentSettingBubbleModel {
   void set_message(const base::string16& message) {
     bubble_content_.message = message;
   }
+  void clear_message() { bubble_content_.message.clear(); }
   void AddListItem(const ListItem& item);
   void RemoveListItem(int index);
   void set_radio_group(const RadioGroup& radio_group) {