Add CHECK in ChromeContentRulesRegistry::AddRulesImpl().

This CL is a sanity check on ChromeContentRulesRegistry::AddRulesImpl()
which will help diagnose system inconsistency issues.

Bug: 1010336
Change-Id: Id4be21a63e966e2b0a81f74183489217b0768ad7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2368613
Commit-Queue: calamity <calamity@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801282}

chrome/browser/extensions/api/declarative_content/chrome_content_rules_registry.cc

@@ -230,8 +230,8 @@ std::string ChromeContentRulesRegistry::AddRulesImpl(
     const std::vector<const api::events::Rule*>& api_rules) {
   EvaluationScope evaluation_scope(this);
   const Extension* extension = ExtensionRegistry::Get(browser_context())
-      ->GetInstalledExtension(extension_id);
-  DCHECK(extension);
+      ->enabled_extensions().GetByID(extension_id);
+  CHECK(extension);
 
   std::string error;
   RulesMap new_rules;