[MD Feedback] Add placeholder feedback entry point.

chrome/browser/feedback/show_feedback_page.cc

Index: chrome/browser/feedback/show_feedback_page.cc
diff --git a/chrome/browser/feedback/show_feedback_page.cc b/chrome/browser/feedback/show_feedback_page.cc
index 4fc24491367956bda62eb2d4546e74647ca0fb1d..0c04809ebb0fd6ce89b219d38deaee5dbdc6da7e 100644
--- a/chrome/browser/feedback/show_feedback_page.cc
+++ b/chrome/browser/feedback/show_feedback_page.cc
@@ -14,6 +14,8 @@
 #include "chrome/browser/ui/browser_finder.h"
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
+#include "chrome/browser/ui/webui/md_feedback/md_feedback_dialog_controller.h"
+#include "chrome/common/chrome_switches.h"
 #include "components/signin/core/account_id/account_id.h"
 #include "content/public/browser/web_contents.h"
 #include "url/gurl.h"
@@ -78,6 +80,11 @@ void ShowFeedbackPage(Browser* browser,
                 : profile;
 #endif
 
+  if (::switches::MdFeedbackEnabled()) {
+    MdFeedbackDialogController::GetInstance()->Show(profile);
+    return;
+  }
+
   extensions::FeedbackPrivateAPI* api =
       extensions::FeedbackPrivateAPI::GetFactoryInstance()->Get(profile);