Allow startup with missing V8 snapshot file.

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 f9d813f525c196b1c136ab259b1e43c9750f7fa6..d282397624ffab47f047a5cb015982235ba82450 100644
--- a/extensions/shell/browser/shell_content_browser_client.h
+++ b/extensions/shell/browser/shell_content_browser_client.h
@@ -52,6 +52,8 @@ class ShellContentBrowserClient : public content::ContentBrowserClient {
   void SiteInstanceDeleting(content::SiteInstance* site_instance) override;
   void AppendExtraCommandLineSwitches(base::CommandLine* command_line,
                                       int child_process_id) override;
+  void AppendMappedFileCommandLineSwitches(
+      base::CommandLine* command_line) override;
   content::SpeechRecognitionManagerDelegate*
   CreateSpeechRecognitionManagerDelegate() override;
   content::BrowserPpapiHost* GetExternalBrowserPpapiHost(
@@ -83,6 +85,8 @@ class ShellContentBrowserClient : public content::ContentBrowserClient {
 #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
 
   // Owned by content::BrowserMainLoop.