Allow startup with missing V8 snapshot file.

chrome/browser/chrome_content_browser_client.h

Index: chrome/browser/chrome_content_browser_client.h
diff --git a/chrome/browser/chrome_content_browser_client.h b/chrome/browser/chrome_content_browser_client.h
index 89f7b2231df55e6944cadf2fbd1804afd7e54e08..92e486de38aba650bb71e4ba31f04ccb3486fa4e 100644
--- a/chrome/browser/chrome_content_browser_client.h
+++ b/chrome/browser/chrome_content_browser_client.h
@@ -112,6 +112,8 @@ class ChromeContentBrowserClient : public content::ContentBrowserClient {
       const std::string& alias_name) override;
   void AppendExtraCommandLineSwitches(base::CommandLine* command_line,
                                       int child_process_id) override;
+  void AppendMappedFileCommandLineSwitches(
+      base::CommandLine* command_line) override;
   std::string GetApplicationLocale() override;
   std::string GetAcceptLangs(content::BrowserContext* context) override;
   const gfx::ImageSkia* GetDefaultFavicon() override;
@@ -304,6 +306,8 @@ class ChromeContentBrowserClient : 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  // OS_POSIX && !OS_MACOSX
 
   // Vector of additional ChromeContentBrowserClientParts.