Allow startup with missing V8 snapshot file.

ash/shell/content_client/shell_content_browser_client.h

 // 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.
 
 #ifndef ASH_SHELL_CONTENT_CLIENT_SHELL_CONTENT_BROWSER_CLIENT_H_
 #define ASH_SHELL_CONTENT_CLIENT_SHELL_CONTENT_BROWSER_CLIENT_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 30 matching lines @@
       int child_process_id,
       content::FileDescriptorInfo* mappings) override;
 #endif
 
   content::ShellBrowserContext* browser_context();
 
  private:
 #if defined(OS_POSIX) && !defined(OS_MACOSX)
   base::ScopedFD v8_natives_fd_;
   base::ScopedFD v8_snapshot_fd_;
+  bool natives_fd_exists() { return v8_natives_fd_ != -1; }
+  bool snapshot_fd_exists() { return v8_snapshot_fd_ != -1; }
 #endif
 
   ShellBrowserMainParts* shell_browser_main_parts_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellContentBrowserClient);
 };
 
 }  // namespace shell
 }  // namespace ash
 
 #endif  // ASH_SHELL_CONTENT_CLIENT_SHELL_CONTENT_BROWSER_CLIENT_H_