Add HeadlessTabSocket

headless/public/headless_browser_context.h

Index: headless/public/headless_browser_context.h
diff --git a/headless/public/headless_browser_context.h b/headless/public/headless_browser_context.h
index 4bdd7a51d7ea8d5b7dc6aced8350c3e237fbf1d4..ec8976b0552957aca9cd4c39127ef7d88575f956 100644
--- a/headless/public/headless_browser_context.h
+++ b/headless/public/headless_browser_context.h
@@ -91,6 +91,8 @@ class HEADLESS_EXPORT HeadlessBrowserContext::Builder {
   Builder& AddJsMojoBindings(const std::string& mojom_name,
                              const std::string& js_bindings);
 
+  Builder& AddTabSocketMojoBindings();
+
   // By default if you add mojo bindings, http and https are disabled because
   // its almost certinly unsafe for arbitary sites on the internet to have
   // access to these bindings.  If you know what you're doing it may be OK to