Enable building headless_shell in MAC. This is an initial implementation with a hidden window, rath…

headless/lib/headless_content_main_delegate.h

Index: headless/lib/headless_content_main_delegate.h
diff --git a/headless/lib/headless_content_main_delegate.h b/headless/lib/headless_content_main_delegate.h
index 35eff70c0077fcabe68a2617566f1b8e63fb0c06..cb33f226d178bf684b7c7f54894b97bf07381b36 100644
--- a/headless/lib/headless_content_main_delegate.h
+++ b/headless/lib/headless_content_main_delegate.h
@@ -35,11 +35,14 @@ class HeadlessContentMainDelegate : public content::ContentMainDelegate {
   int RunProcess(
       const std::string& process_type,
       const content::MainFunctionParams& main_function_params) override;
-  void ZygoteForked() override;
   content::ContentBrowserClient* CreateContentBrowserClient() override;
 
   HeadlessBrowserImpl* browser() const { return browser_.get(); }
 
+#if !defined(OS_MACOSX) && defined(OS_POSIX) && !defined(OS_ANDROID)
+  void ZygoteForked() override;
+#endif
+
  private:
   friend class HeadlessBrowserTest;