Swap main menu with app-specific menu when app window focused.

chrome/browser/ui/cocoa/browser_window_controller.mm

Index: chrome/browser/ui/cocoa/browser_window_controller.mm
diff --git a/chrome/browser/ui/cocoa/browser_window_controller.mm b/chrome/browser/ui/cocoa/browser_window_controller.mm
index 6f70d9ff33e377ea7ab30c0b03ed55d5fda63f15..523005bbfc95e420a0064158a6822c7f01a53132 100644
--- a/chrome/browser/ui/cocoa/browser_window_controller.mm
+++ b/chrome/browser/ui/cocoa/browser_window_controller.mm
@@ -13,6 +13,7 @@
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/app/chrome_command_ids.h"  // IDC_*
+#include "chrome/browser/app_controller_mac.h"
 #include "chrome/browser/bookmarks/bookmark_model_factory.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/devtools/devtools_window.h"
@@ -655,6 +656,7 @@ enum {
     if (RenderWidgetHostView* rwhv = contents->GetRenderWidgetHostView())
       rwhv->SetActive(true);
   }
+  [[NSApp delegate] setMenuBarToChrome];
 }
 
 // Called when we are deactivated (when we lose focus).