[Extensions] Make chrome://extensions use developerPrivate for packing crxs

chrome/browser/extensions/api/developer_private/entry_picker.cc

Index: chrome/browser/extensions/api/developer_private/entry_picker.cc
diff --git a/chrome/browser/extensions/api/developer_private/entry_picker.cc b/chrome/browser/extensions/api/developer_private/entry_picker.cc
index 9e3b6af84d5ca7b96bd9cc1e9e7d5df4af1b703f..9baaa1ec14f7e48cf97e87a83ac9de5f6e700a93 100644
--- a/chrome/browser/extensions/api/developer_private/entry_picker.cc
+++ b/chrome/browser/extensions/api/developer_private/entry_picker.cc
@@ -79,6 +79,13 @@ void EntryPicker::FileSelectionCanceled(void* params) {
   delete this;
 }
 
+void EntryPicker::MultiFilesSelected(const std::vector<base::FilePath>& files,
+                                     void* params) {
+  NOTREACHED();
+  client_->FileSelectionCanceled();
+  delete this;
+}
+
 // static
 void EntryPicker::SkipPickerAndAlwaysSelectPathForTest(
     base::FilePath* path) {