app_shell: Fix PrefsTabHelper dependency of ExtensionHost

chrome/browser/extensions/chrome_extensions_browser_client.cc

Index: chrome/browser/extensions/chrome_extensions_browser_client.cc
diff --git a/chrome/browser/extensions/chrome_extensions_browser_client.cc b/chrome/browser/extensions/chrome_extensions_browser_client.cc
index f6b129246f6011c42ab595d6cccefca3204a14f1..3bdf48cea68b76e8e829a18759f5eb177a264152 100644
--- a/chrome/browser/extensions/chrome_extensions_browser_client.cc
+++ b/chrome/browser/extensions/chrome_extensions_browser_client.cc
@@ -14,6 +14,7 @@
 #include "chrome/browser/profiles/profile_manager.h"
 #include "chrome/browser/ui/app_modal_dialogs/javascript_dialog_manager.h"
 #include "chrome/browser/ui/browser_finder.h"
+#include "chrome/browser/ui/prefs/prefs_tab_helper.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/chrome_version_info.h"
 #include "chrome/common/pref_names.h"
@@ -108,6 +109,11 @@ bool ChromeExtensionsBrowserClient::IsBackgroundPageAllowed(
   return true;
 }
 
+void ChromeExtensionsBrowserClient::OnExtensionHostCreated(
+    content::WebContents* web_contents) {
+  PrefsTabHelper::CreateForWebContents(web_contents);
+}
+
 bool ChromeExtensionsBrowserClient::DidVersionUpdate(
     content::BrowserContext* context) {
   Profile* profile = static_cast<Profile*>(context);