Implement a poor man's PostAfterStartupTask() function.

chrome/browser/chrome_content_browser_client.h

Index: chrome/browser/chrome_content_browser_client.h
diff --git a/chrome/browser/chrome_content_browser_client.h b/chrome/browser/chrome_content_browser_client.h
index 30e8f4144d1580050b7ef3ed0f6af0007200160c..43b2d630942f8f7bdac6d2f042b157167883c2d8 100644
--- a/chrome/browser/chrome_content_browser_client.h
+++ b/chrome/browser/chrome_content_browser_client.h
@@ -54,6 +54,10 @@ class ChromeContentBrowserClient : public content::ContentBrowserClient {
 
   content::BrowserMainParts* CreateBrowserMainParts(
       const content::MainFunctionParams& parameters) override;
+  void PostAfterStartupTask(
+      const tracked_objects::Location& from_here,
+      const scoped_refptr<base::TaskRunner>& task_runner,
+      const base::Closure& task) override;
   std::string GetStoragePartitionIdForSite(
       content::BrowserContext* browser_context,
       const GURL& site) override;