Add support to extension_shell and ash_shell to use external V8 snapshot files.

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 15 matching lines @@
   ShellContentBrowserClient();
   ~ShellContentBrowserClient() override;
 
   // Overridden from content::ContentBrowserClient:
   content::BrowserMainParts* CreateBrowserMainParts(
       const content::MainFunctionParams& parameters) override;
   net::URLRequestContextGetter* CreateRequestContext(
       content::BrowserContext* browser_context,
       content::ProtocolHandlerMap* protocol_handlers,
       content::URLRequestInterceptorScopedVector request_interceptors) override;
+#if defined(OS_POSIX) && !defined(OS_MACOSX)
+  void GetAdditionalMappedFilesForChildProcess(
+      const base::CommandLine& command_line,
+      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_;
+#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_