[Extensions] Clean up renderer channel-related code

chrome/browser/extensions/chrome_extensions_browser_client.h

Index: chrome/browser/extensions/chrome_extensions_browser_client.h
diff --git a/chrome/browser/extensions/chrome_extensions_browser_client.h b/chrome/browser/extensions/chrome_extensions_browser_client.h
index 901c0a795eb3ab9f1d457807ddc262574d3c55e2..100c78f508f330d2cb1798b419b3c2750d293397 100644
--- a/chrome/browser/extensions/chrome_extensions_browser_client.h
+++ b/chrome/browser/extensions/chrome_extensions_browser_client.h
@@ -14,7 +14,6 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "build/build_config.h"
-#include "chrome/browser/extensions/chrome_notification_observer.h"
 #include "extensions/browser/extensions_browser_client.h"
 
 namespace base {
@@ -126,9 +125,6 @@ class ChromeExtensionsBrowserClient : public ExtensionsBrowserClient {
  private:
   friend struct base::DefaultLazyInstanceTraits<ChromeExtensionsBrowserClient>;
 
-  // Observer for Chrome-specific notifications.
-  ChromeNotificationObserver notification_observer_;
-
   // Support for ProcessManager.
   std::unique_ptr<ChromeProcessManagerDelegate> process_manager_delegate_;