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

extensions/shell/browser/shell_content_browser_client.h

Index: extensions/shell/browser/shell_content_browser_client.h
diff --git a/extensions/shell/browser/shell_content_browser_client.h b/extensions/shell/browser/shell_content_browser_client.h
index 16e51ca448516b202795243a245d02c085e75a2f..f9d813f525c196b1c136ab259b1e43c9750f7fa6 100644
--- a/extensions/shell/browser/shell_content_browser_client.h
+++ b/extensions/shell/browser/shell_content_browser_client.h
@@ -58,6 +58,13 @@ class ShellContentBrowserClient : public content::ContentBrowserClient {
       int plugin_process_id) override;
   void GetAdditionalAllowedSchemesForFileSystem(
       std::vector<std::string>* additional_schemes) 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::DevToolsManagerDelegate* GetDevToolsManagerDelegate() override;
 
  protected:
@@ -73,6 +80,11 @@ class ShellContentBrowserClient : public content::ContentBrowserClient {
   // Returns the extension or app associated with |site_instance| or NULL.
   const Extension* GetExtension(content::SiteInstance* site_instance);
 
+#if defined(OS_POSIX) && !defined(OS_MACOSX)
+  base::ScopedFD v8_natives_fd_;
+  base::ScopedFD v8_snapshot_fd_;
+#endif
+
   // Owned by content::BrowserMainLoop.
   ShellBrowserMainParts* browser_main_parts_;