Don't use plugin-specific content settings that are from user prefs

chrome/browser/plugins/plugin_utils.cc

Index: chrome/browser/plugins/plugin_utils.cc
diff --git a/chrome/browser/plugins/plugin_utils.cc b/chrome/browser/plugins/plugin_utils.cc
index bdf177b1aa6dc0a0e91940666dca568258fcbc91..3241dd6fc889e303d529d761c5a111e80eff658f 100644
--- a/chrome/browser/plugins/plugin_utils.cc
+++ b/chrome/browser/plugins/plugin_utils.cc
@@ -72,10 +72,16 @@ void GetPluginContentSettingInternal(
         host_content_settings_map->GetWebsiteSetting(
             policy_url, plugin_url, CONTENT_SETTINGS_TYPE_PLUGINS,
             std::string(), &general_info);
-    // If there is a plugin-specific setting, we use it, unless the general
-    // setting was set by policy, in which case it takes precedence.
+    // The order of precedence is:
+    // -If a general setting was set by policy, use it.
+    // -If there is a plugin-specific setting which is not user provided (e.g.
+    //  it comes from an extension or some other source), use it. We don't use
+    //  user-provided plugin-specific settings because there is no longer any UI
+    //  to set them.
+    // -Otherwise use the general setting.
     uses_plugin_specific_setting =
         specific_setting &&
+        specific_info.source != content_settings::SETTING_SOURCE_USER &&
         general_info.source != content_settings::SETTING_SOURCE_POLICY;
     if (uses_plugin_specific_setting) {
       value = std::move(specific_setting);