Implement RunFileChooser for ExtensionHost, so that file input elements work in

chrome/browser/file_select_helper.cc

Index: chrome/browser/file_select_helper.cc
diff --git a/chrome/browser/file_select_helper.cc b/chrome/browser/file_select_helper.cc
index 1b7eda1b1f94179b2c8259d72e3dc277b4b00dfa..d6d73f75abf0eaf7c7561b0d071dab69eb496386 100644
--- a/chrome/browser/file_select_helper.cc
+++ b/chrome/browser/file_select_helper.cc
@@ -301,8 +301,12 @@ void FileSelectHelper::RunFileChooserOnFileThread(
 
 void FileSelectHelper::RunFileChooserOnUIThread(
     const content::FileChooserParams& params) {
-  if (!render_view_host_ || !tab_contents_)
+  if (!render_view_host_ || !tab_contents_) {
+    // If the renderer was destroyed before we started, just cancel the
+    // operation.
+    RunFileChooserEnd();
     return;
+  }
 
   if (!select_file_dialog_.get())
     select_file_dialog_ = SelectFileDialog::Create(this);