[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..19b0216f06365ea77667ff9f46019ddcf9e7de59 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 +80,13 @@ void ShowFeedbackPage(Browser* browser,
                 : profile;
 #endif
 
+  if (::switches::MdFeedbackEnabled()) {
+    MdFeedbackDialogController* controller =
+        MdFeedbackDialogController::GetOrCreate();

[afakhry, 2016/08/02 22:15:56]

It's actually GetOrCreateAndGet() ;)
To be consistent with the rest of the code in the codebase, where Get() or
GetInstance() are far more common, you might want to call it just Get() and then
shorten your code like:

MdFeedbackDialogController::Get()->Show(profile);

[apacible, 2016/08/09 22:11:13]

Done.

+    controller->Show(profile);
+    return;
+  }
+
   extensions::FeedbackPrivateAPI* api =
       extensions::FeedbackPrivateAPI::GetFactoryInstance()->Get(profile);