Reset |set_should_auto_open_bubble| when updating Media Image Model

Previously once the auto_open bubble was set it was never reset so it
continued to pop up until the browser was closed. This change resets
that on every update so it only prompts when the user selects allow on
the per site permission prompt.

Bug: 1111087
Change-Id: Ic377cfa8b764a577eaa5acbf0d416865360465fe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2327467Reviewed-by: Balazs Engedy <engedy@chromium.org>
Commit-Queue: Balazs Engedy <engedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#793177}

chrome/browser/ui/content_settings/content_setting_image_model.cc

@@ -626,6 +626,7 @@ ContentSettingMediaImageModel::ContentSettingMediaImageModel()
 
 bool ContentSettingMediaImageModel::UpdateAndGetVisibility(
     WebContents* web_contents) {
+  set_should_auto_open_bubble(false);
   TabSpecificContentSettings* content_settings =
       TabSpecificContentSettings::FromWebContents(web_contents);
   if (!content_settings)