Make the theme install infobar have an 'undo' button instead of

chrome/browser/extensions/theme_preview_infobar_delegate.cc

 // Copyright (c) 2009 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/extensions/theme_preview_infobar_delegate.h"
 
 #include "app/l10n_util.h"
 #include "base/string_util.h"
+#include "chrome/browser/extensions/extensions_service.h"
 #include "chrome/browser/profile.h"
 #include "chrome/browser/tab_contents/tab_contents.h"
+#include "chrome/common/extensions/extension.h"
 #include "grit/generated_resources.h"
 
 ThemePreviewInfobarDelegate::ThemePreviewInfobarDelegate(
-    TabContents* tab_contents, const std::string& name)
+    TabContents* tab_contents, const std::string& name,
+    const std::string& previous_theme_id)
          : ConfirmInfoBarDelegate(tab_contents),
-           profile_(tab_contents->profile()), name_(name) {
+           profile_(tab_contents->profile()), name_(name),
+           previous_theme_id_(previous_theme_id) {
 }
 
 void ThemePreviewInfobarDelegate::InfoBarClosed() {
   delete this;
 }
 
 std::wstring ThemePreviewInfobarDelegate::GetMessageText() const {
   return l10n_util::GetStringF(IDS_THEME_INSTALL_INFOBAR_LABEL,
                                UTF8ToWide(name_));
 }
@@ skipping 17 matching lines @@
     ConfirmInfoBarDelegate::InfoBarButton button) const {
   switch (button) {
     case BUTTON_CANCEL:
       return l10n_util::GetString(IDS_THEME_INSTALL_INFOBAR_UNDO_BUTTON);
     default:
       return L"";
   }
 }
 
 bool ThemePreviewInfobarDelegate::Cancel() {
-  // Blech, this is a total hack.
-  //
-  // a) We should be uninstalling via ExtensionsService, not
-  //    Profile::ClearTheme().
-  // b) We should be able to view the theme without installing it. This would
-  //    help in edge cases like the user closing the window or tab before making
-  //    a decision.
+  if (!previous_theme_id_.empty()) {
+    ExtensionsService* service = profile_->GetExtensionsService();
+    if (service) {
+      Extension* previous_theme = service->GetExtensionById(previous_theme_id_);
+      if (previous_theme) {
+        profile_->SetTheme(previous_theme);
+        return true;
+      }
+    }
+  }
+
   profile_->ClearTheme();
   return true;
 }