mustash: Remove NOTREACHED() so navigation does not crash

content/browser/renderer_host/render_widget_host_view_mus.cc

Index: content/browser/renderer_host/render_widget_host_view_mus.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_mus.cc b/content/browser/renderer_host/render_widget_host_view_mus.cc
index 8a12e156e7579eebcb81a6de935a2804f4a0e5a9..bc0ae255fdd4a46e10f1bd144bba152dc3a8026a 100644
--- a/content/browser/renderer_host/render_widget_host_view_mus.cc
+++ b/content/browser/renderer_host/render_widget_host_view_mus.cc
@@ -202,7 +202,8 @@ void RenderWidgetHostViewMus::CopyFromCompositingSurface(
     const gfx::Size& /* dst_size */,
     const ReadbackRequestCallback& callback,
     const SkColorType /* preferred_color_type */) {
-  NOTREACHED();
+  // TODO(fsamuel): Implement read back.
+  NOTIMPLEMENTED();
   callback.Run(SkBitmap(), READBACK_FAILED);
 }