Make //mojo/edk/js a component.

mojo/edk/js/threading.h

Index: mojo/edk/js/threading.h
diff --git a/mojo/edk/js/threading.h b/mojo/edk/js/threading.h
index 10404d5bc778e95ab3cfdb9d65fdc989e07fefd8..653d0765a6971f407abe3c51d282b4bf58772eba 100644
--- a/mojo/edk/js/threading.h
+++ b/mojo/edk/js/threading.h
@@ -6,13 +6,14 @@
 #define MOJO_EDK_JS_THREADING_H_
 
 #include "gin/public/wrapper_info.h"
+#include "mojo/edk/js/js_export.h"
 #include "v8/include/v8.h"
 
 namespace mojo {
 namespace edk {
 namespace js {
 
-class Threading {
+class MOJO_JS_EXPORT Threading {
  public:
   static const char kModuleName[];
   static v8::Local<v8::Value> GetModule(v8::Isolate* isolate);