Fix a crash on clicking "Load unpacked extension" multiple times

chrome/browser/ui/webui/extensions/extension_loader_handler.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/webui/extensions/extension_loader_handler.h"
 
 #include "base/bind.h"
 #include "base/files/file_util.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
@@ skipping 81 matching lines @@
   // it doesn't try and call back.
   if (load_extension_dialog_.get())
     load_extension_dialog_->ListenerDestroyed();
 }
 
 void ExtensionLoaderHandler::FileHelper::ChooseFile() {
   static const int kFileTypeIndex = 0;  // No file type information to index.
   static const ui::SelectFileDialog::Type kSelectType =
       ui::SelectFileDialog::SELECT_FOLDER;
 
+  gfx::NativeWindow parent_window =
+      loader_handler_->web_ui()->GetWebContents()->GetTopLevelNativeWindow();
   if (!load_extension_dialog_.get()) {
     load_extension_dialog_ = ui::SelectFileDialog::Create(
         this,
         new ChromeSelectFilePolicy(
             loader_handler_->web_ui()->GetWebContents()));
+  } else if (load_extension_dialog_->IsRunning(parent_window)) {
+    LOG(ERROR) << "Select file dialog already in use!";

[Devlin, 2014/12/04 21:39:10]

Generally, we don't like to log errors for things that can happen in the normal
course of action.  Since we should be able to handle the user clicking on the
load button twice, I'd remove this in favor of a comment
// File chooser dialog is already running; ignore the click.

+    return;
   }
 
   load_extension_dialog_->SelectFile(
       kSelectType,
       title_,
       last_unpacked_directory_,
       NULL,
       kFileTypeIndex,
       base::FilePath::StringType(),
-      loader_handler_->web_ui()->GetWebContents()->GetTopLevelNativeWindow(),
+      parent_window,
       NULL);
 
   content::RecordComputedAction("Options_LoadUnpackedExtension");
 }
 
 void ExtensionLoaderHandler::FileHelper::FileSelected(
     const base::FilePath& path, int index, void* params) {
   loader_handler_->LoadUnpackedExtensionImpl(path);
 }
 
@@ skipping 174 matching lines @@
 }
 
 void ExtensionLoaderHandler::NotifyFrontendOfFailure() {
   web_ui()->CallJavascriptFunction(
       "extensions.ExtensionLoader.notifyLoadFailed",
       failures_);
   failures_.Clear();
 }
 
 }  // namespace extensions