Fix the browser crash when changing wallpaper with chrome.wallpaper API.

chrome/browser/chromeos/extensions/wallpaper_api.cc

 // Copyright 2013 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/chromeos/extensions/wallpaper_api.h"
 
 #include <string>
 #include <utility>
 #include <vector>
 
@@ skipping 230 matching lines @@
   }
 
   // Inform the native Wallpaper Picker Application that the current wallpaper
   // has been modified by a third party application.
   if (extension()->id() != extension_misc::kWallpaperManagerId) {
     Profile* profile = Profile::FromBrowserContext(browser_context());
     extensions::EventRouter* event_router =
         extensions::EventRouter::Get(profile);
     std::unique_ptr<base::ListValue> event_args(new base::ListValue());
     event_args->Append(original_result);
-    event_args->Append(thumbnail_result);
+    event_args->Append(thumbnail_result->DeepCopy());
     event_args->Append(new base::StringValue(
         extensions::api::wallpaper::ToString(params_->details.layout)));
     // Setting wallpaper from right click menu in 'Files' app is a feature that
     // was implemented in crbug.com/578935. Since 'Files' app is a built-in v1
     // app in ChromeOS, we should treat it slightly differently with other third
     // party apps: the wallpaper set by the 'Files' app should still be syncable
     // and it should not appear in the wallpaper grid in the Wallpaper Picker.
     // But we should not display the 'wallpaper-set-by-mesage' since it might
     // introduce confusion as shown in crbug.com/599407.
     event_args->Append(new base::StringValue(
@@ skipping 15 matching lines @@
     const std::string& response) {
   if (success) {
     params_->details.data.reset(
         new std::vector<char>(response.begin(), response.end()));
     StartDecode(*params_->details.data);
   } else {
     SetError(response);
     SendResponse(false);
   }
 }