Extract external file systems handling from isolated context.

chrome/browser/extensions/api/file_system/file_system_api.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/extensions/api/file_system/file_system_api.h"
 
 #include "base/bind.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/logging.h"
@@ skipping 138 matching lines @@
   if (!policy->CanReadFileSystem(render_view_host->GetProcess()->GetID(),
                                  filesystem_id)) {
     *error = kSecurityError;
     return false;
   }
 
   IsolatedContext* context = IsolatedContext::GetInstance();
   FilePath relative_path = FilePath::FromUTF8Unsafe(filesystem_path);
   FilePath virtual_path = context->CreateVirtualRootPath(filesystem_id)
       .Append(relative_path);
-  if (!context->CrackIsolatedPath(virtual_path,
-                                  &filesystem_id,
-                                  NULL,
-                                  file_path)) {
+  if (!context->CrackVirtualPath(virtual_path,
+                                 &filesystem_id,
+                                 NULL,
+                                 file_path)) {
     *error = kInvalidParameters;
     return false;
   }
 
   return true;
 }
 
 bool DoCheckWritableFile(const FilePath& path) {
   // Don't allow links.
   if (file_util::PathExists(path) && file_util::IsLink(path))
@@ skipping 417 matching lines @@
 
   if (entry_type == WRITABLE && !HasFileSystemWritePermission()) {
     error_ = kRequiresFileSystemWriteError;
     return false;
   }
 
   return ShowPicker(suggested_name, file_type_info, picker_type, entry_type);
 }
 
 }  // namespace extensions