Use extension-based file picker from CrOS for Aura builds.

chrome/browser/ui/views/shell_dialogs_aura.cc

Index: chrome/browser/ui/views/shell_dialogs_aura.cc
diff --git a/chrome/browser/ui/views/shell_dialogs_aura.cc b/chrome/browser/ui/views/shell_dialogs_aura.cc
index b3f10d0eafced5c609bddf6b804bcd9baa51fe4d..2548b9a34c17a376754c29596dd13773e78732a6 100644
--- a/chrome/browser/ui/views/shell_dialogs_aura.cc
+++ b/chrome/browser/ui/views/shell_dialogs_aura.cc
@@ -4,7 +4,11 @@
 
 #include "chrome/browser/ui/shell_dialogs.h"
 
+#include "chrome/browser/ui/views/file_manager_dialog.h"
+#include "content/browser/browser_thread.h"
+
 // static
 SelectFileDialog* SelectFileDialog::Create(Listener* listener) {
-  return NULL;
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  return new FileManagerDialog(listener);
 }