Add --enable-show-modal-dialog to chrome

chrome/renderer/chrome_render_process_observer.cc

Index: chrome/renderer/chrome_render_process_observer.cc
diff --git a/chrome/renderer/chrome_render_process_observer.cc b/chrome/renderer/chrome_render_process_observer.cc
index 33d6678cce9be2523b41889f70f1f62c515cd41c..2e4e54bf0176ac47cbcf1f953074227d1788be12 100644
--- a/chrome/renderer/chrome_render_process_observer.cc
+++ b/chrome/renderer/chrome_render_process_observer.cc
@@ -262,6 +262,9 @@ ChromeRenderProcessObserver::ChromeRenderProcessObserver(
   WebRuntimeFeatures::enableRequestAutocomplete(true);
 #endif
 
+  if (command_line.HasSwitch(switches::kEnableShowModalDialog))
+    WebRuntimeFeatures::enableShowModalDialog(true);
+
   RenderThread* thread = RenderThread::Get();
   resource_delegate_.reset(new RendererResourceDelegate());
   thread->SetResourceDispatcherDelegate(resource_delegate_.get());