Add null check to ContentAction::Apply.

This CL is a speculative fix for a Feedback App crash.

Bug: 1010336
Change-Id: Ifc97455fbf942af41dc54417cc7449b888577d32
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2210602Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: calamity <calamity@chromium.org>
Auto-Submit: calamity <calamity@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774999}

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

@@ -73,11 +73,24 @@ class ShowExtensionAction : public ContentAction {
       *error = kNoAction;
       return nullptr;
     }
-    return std::make_unique<ShowExtensionAction>();
+
+    auto action = std::make_unique<ShowExtensionAction>();
+    // Sanity check for https://crbug.com/1010336.
+    // |browser_context| is null in unit tests.
+    CHECK(!browser_context || action->GetAction(browser_context, extension));
+    return action;
   }
 
   // Implementation of ContentAction:
   void Apply(const ApplyInfo& apply_info) const override {
+    // Sanity check for https://crbug.com/1010336.
+    // This check fails on the 2 cases that could cause
+    // ExtensionActionManager::GetExtensionAction to return null so we can
+    // understand null-related crashes.
+    CHECK(ActionInfo::GetExtensionActionInfo(apply_info.extension));
+    CHECK(ExtensionRegistry::Get(apply_info.browser_context)
+              ->enabled_extensions()
+              .Contains(apply_info.extension->id()));
     ExtensionAction* action =
         GetAction(apply_info.browser_context, apply_info.extension);
     action->DeclarativeShow(ExtensionTabUtil::GetTabId(apply_info.tab));