Make URLDataSource::GetSource() const.

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

 // Copyright (c) 2012 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_icon_source.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/stl_util.h"
@@ skipping 87 matching lines @@
   std::string contents = ResourceBundle::GetSharedInstance()
       .GetRawDataResourceForScale(resource_id,
                                   ui::SCALE_FACTOR_100P).as_string();
 
   // Convert and return it.
   const unsigned char* data =
       reinterpret_cast<const unsigned char*>(contents.data());
   return ToBitmap(data, contents.length());
 }
 
-std::string ExtensionIconSource::GetSource() {
+std::string ExtensionIconSource::GetSource() const {
   return chrome::kChromeUIExtensionIconHost;
 }
 
 std::string ExtensionIconSource::GetMimeType(const std::string&) const {
   // We need to explicitly return a mime type, otherwise if the user tries to
   // drag the image they get no extension.
   return "image/png";
 }
 
 void ExtensionIconSource::StartDataRequest(
@@ skipping 218 matching lines @@
 
 void ExtensionIconSource::ClearData(int request_id) {
   std::map<int, ExtensionIconRequest*>::iterator i =
       request_map_.find(request_id);
   if (i == request_map_.end())
     return;
 
   delete i->second;
   request_map_.erase(i);
 }