Support sync loading of the initial bundle/source

Reviewed By: javache

Differential Revision: D3897521

fbshipit-source-id: a4f234c7003a5f4be952d315eb62f382836e24dc

ReactCommon/cxxreact/NativeToJsBridge.h

@@ -44,9 +44,12 @@ public:
 class JsToNativeBridge;
 
 // This class manages calls from native code to JS.  It also manages
-// executors and their threads.  This part is used by both bridges for
-// now, but further refactorings should separate the bridges more
-// fully #11247981.
+// executors and their threads.  All functions here can be called from
+// any thread.
+//
+// Except for loadApplicationScriptSync(), all void methods will queue
+// work to run on the jsQueue passed to the ctor, and return
+// immediately.
 class NativeToJsBridge {
 public:
   friend class JsToNativeBridge;
@@ -86,6 +89,10 @@ public:
     std::unique_ptr<JSModulesUnbundle> unbundle,
     std::unique_ptr<const JSBigString> startupCode,
     std::string sourceURL);
+  void loadApplicationSync(
+    std::unique_ptr<JSModulesUnbundle> unbundle,
+    std::unique_ptr<const JSBigString> startupCode,
+    std::string sourceURL);
 
   /**
    * Similar to loading a "bundle", but instead of passing js source this method accepts