Implement a MusBrowserFrame.

chrome/browser/ui/views/frame/browser_view.cc

Index: chrome/browser/ui/views/frame/browser_view.cc
diff --git a/chrome/browser/ui/views/frame/browser_view.cc b/chrome/browser/ui/views/frame/browser_view.cc
index e6665e734e8b830210f85e2e6c2d8dd3b7ec4593..1f5f3022bf2b226a334ca606f029a53f2b0b3efa 100644
--- a/chrome/browser/ui/views/frame/browser_view.cc
+++ b/chrome/browser/ui/views/frame/browser_view.cc
@@ -26,6 +26,7 @@
 #include "chrome/browser/extensions/extension_util.h"
 #include "chrome/browser/extensions/tab_helper.h"
 #include "chrome/browser/infobars/infobar_service.h"
+#include "chrome/browser/mojo_runner_util.h"
 #include "chrome/browser/native_window_notification_source.h"
 #include "chrome/browser/profiles/avatar_menu.h"
 #include "chrome/browser/profiles/profile.h"
@@ -2382,6 +2383,12 @@ bool BrowserView::ShouldUseImmersiveFullscreenForUrl(const GURL& url) const {
 }
 
 void BrowserView::LoadAccelerators() {
+  // TODO(beng): for some reason GetFocusManager() returns null in this case,
+  //             investigate, but for now just disable accelerators in this
+  //             mode.
+  if (IsRunningInMojoRunner())
+    return;
+
   views::FocusManager* focus_manager = GetFocusManager();
   DCHECK(focus_manager);